Re: [time-nuts] Effect of EFC noise on phase noise
Ja Gerhard, bitte schicke mir den LTSpice file, Danke im Voraus und 73 KJ6UHN Alex On 8/1/2016 6:34 PM, Gerhard Hoffmann wrote: Am 02.08.2016 um 02:42 schrieb Bruce Griffiths: /"I'm working on a new amplifier based on IF3602 or BF862 FETs that can use 10u foil only."/ / / Similar to that published by Groner in Linear Audio? / / I know that Groner exists from some web site, but had no personal contact. Also I don't read Linear Audio other than 2 articles from Scott Wurcer that I've bought. I highly regard Scott, he's the father of the AD797 after all and AD fellow. I also had some conversations with him on that. The preamp will be classical. Some JFETs in parallel, no source resistors except half an Ohm for feedback, more would add to the input noise voltage. Cascode with a Zetex bipolar (or whatever they are called now). OP37 for loop gain. feedback from OP37 output for 50 or 60 dB gain. Post amplifier to 80 db or so. Without the cascode, the 1 MHz is not possible. It does not help that the feedback limits the voltage excursions on the drain. I'm not yet sure about the effective input capacitance. I get abt. 1 or 1.5 MHz bandwidth from a low impedance source. A few nF on the input capacitance would be ok, in the end I want it after a ring mixer for phase noise measurements but I get unreasonably more in simulation, depending on if I measure it from upper frequency corner with a larger input resistor or the resonance frequency with an added inductor. You can get the LTspice file if you like. regards, Gerhard ___ 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. - No virus found in this message. Checked by AVG - www.avg.com Version: 2016.0.7690 / Virus Database: 4627/12724 - Release Date: 08/01/16 ___ 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] Effect of EFC noise on phase noise
Am 02.08.2016 um 02:42 schrieb Bruce Griffiths: /"I'm working on a new amplifier based on IF3602 or BF862 FETs that can use 10u foil only."/ / / Similar to that published by Groner in Linear Audio? / / I know that Groner exists from some web site, but had no personal contact. Also I don't read Linear Audio other than 2 articles from Scott Wurcer that I've bought. I highly regard Scott, he's the father of the AD797 after all and AD fellow. I also had some conversations with him on that. The preamp will be classical. Some JFETs in parallel, no source resistors except half an Ohm for feedback, more would add to the input noise voltage. Cascode with a Zetex bipolar (or whatever they are called now). OP37 for loop gain. feedback from OP37 output for 50 or 60 dB gain. Post amplifier to 80 db or so. Without the cascode, the 1 MHz is not possible. It does not help that the feedback limits the voltage excursions on the drain. I'm not yet sure about the effective input capacitance. I get abt. 1 or 1.5 MHz bandwidth from a low impedance source. A few nF on the input capacitance would be ok, in the end I want it after a ring mixer for phase noise measurements but I get unreasonably more in simulation, depending on if I measure it from upper frequency corner with a larger input resistor or the resonance frequency with an added inductor. You can get the LTspice file if you like. regards, Gerhard ___ 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] Effect of EFC noise on phase noise
"I'm working on a new amplifier based on IF3602 or BF862 FETs that can use 10u foil only." Similar to that published by Groner in Linear Audio? Bruce On Tuesday, 2 August 2016 12:12 PM, Gerhard Hoffmann wrote: Am 01.08.2016 um 22:16 schrieb David: > This duplicates the problems encountered when trying to quantify low > frequency noise from a voltage reference; it is difficult to make an > low frequency high pass filter with lower noise than the lowest noise > references and the capacitor is the problem. I beg to differ. Voltage references are not that wonderful. Bandgaps live from amplifying small voltage differences and stable Zener references at 6 to 7 Volts are plagued by avalanche noise. And that includes the LT6655 band gap. WRT short term stability all of these are eclipsed by 2.7 / 3.3 volt zeners and by LEDs. Even the LT6655 gains a lot of noise performance from an active filter with AD797 / ADA4898 op amps and even resistors and 6V/1000uF Nipon Chemi SMD electrolytics. I have made some absolute noise voltage measurements: < https://www.flickr.com/photos/137684711@N07/albums/72157662535945536 > LEDs and Zeners are measured with bias from a 1 or 2k wire resistor and a 14V NiMH battery. I find the HLMP6000 LED really impressive and the LT3042 regulator. The preamp is 20 ADA4898 op amps in parallel ( i.e. 220pV/sqrtHz), the 0 dB line is 1 nV/sqrt Hz. Everything was fed from batteries in a box in box in a box and then after +80 dB passed to an 89441A vector signal analyzer. The input capacitor of the preamp is 20 times 10uF WIMA foil, that is not enough for the low frequency corner as we do not see the real 1/f noise below 20 Hz. What we see looks more like GR noise, spectrum-wise, and it is really the insufficient shorting of the 10K bias resistor through the input source and coupling cap. I have bought some wet slug tantals as proposed by Jim Williams (see below), 1 uF bring the right 1/f behaviour but at very substantial cost :-( At least for small input voltages alu electrolytics do not seem to make a difference. I did not test large voltages. I'm working on a new amplifier based on IF3602 or BF862 FETs that can use 10u foil only. When it's done I'll repeat these measurements. > In Linear Technology Application Note 124, Jim Williams discusses the > problems with electrolytic capacitors for this type of application. I > have read that you *can* get away with aluminum electrolytics if you > grade them for low leakage and low noise. The dielectric absorption > is also a problem unless you can wait hours for best performance. JW has the added handicap that he wants to keep the the long term and absolute stability of his reference and so cannot afford any voltage drop on a series R. We do not share that problem on an EFC line because the C stands for control and if the voltage there does never change for some other reason we have probably made a bad decision with regard to loop gain. And large resistors may feature more noise voltage, but that increases only with the root of the resistance. The filter corner drops in a linear way, so a large resistor may really help. The tiny noise voltage of a reasonable resistor must be seen anyway in the context of say, a 10811A that tunes +- 1 Hz for 10 Volts on the EFC. regards, Gerhard ___ 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] Effect of EFC noise on phase noise
davidwh...@gmail.com said: > I always thought they should bring the varactor or EFC ground out as a > separate pin but I assume that since they do not, ground noise at least > within the oscillator does not limit performance. I'm pretty sure I've seen comments, probably on this list, about troubles from heater current on a shared ground pin. -- These are my opinions. I hate spam. ___ 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] Effect of EFC noise on phase noise
Hi Ultimately the EFC signal gets to one or more varicap diodes. It likely goes through a bias or attenuator network to get there. Playing with the resistors in the network allows the manufacturer to produce parts with consistent EFC properties. The pinout of your standard OCXO and it’s single ground lies almost entirely with the OEM customers who buy a lot of OCXO’s. To them a minimum number of pins means a minimum amount of hassle. Given the choice between a multi ground part and a single pin, the choice will alway go to the single pin. “We just hook them all to the same point anyway … why the extra pins?”….. Presented wth an app note and the explanation of why, the answer is still “we don’t have time to design that in”. Yes it’s a scary world out there. Bob > On Aug 1, 2016, at 6:40 PM, David wrote: > > Are the EFC inputs all directly DC coupled to the varactor diodes > making them high DC impedance? > > I always thought they should bring the varactor or EFC ground out as a > separate pin but I assume that since they do not, ground noise at > least within the oscillator does not limit performance. > > In the past when I have had low frequency ground noise, I have either > used an instrumentation amplifier at the load or used a high impedance > current source with a load resistor to ground at the load. But I have > difficulty imagining either being used to drive an EFC input because > close proximity of the driving circuit allows it to use the oscillator > ground as a single point ground. > > I wonder if there is anything to be learned by studying how the old > varactor based (parametric) operational amplifiers were used. > > On Mon, 1 Aug 2016 16:32:35 -0400, you wrote: > >> Hi >> >> If you wire up all the possible circuits and check them all out > the >> answer is that big C / small R wins. Big R gets you into resistor noise >> issues >> and stray pickup. >> >> Bob >> >>> On Aug 1, 2016, at 4:16 PM, David wrote: >>> >>> This duplicates the problems encountered when trying to quantify low >>> frequency noise from a voltage reference; it is difficult to make an >>> low frequency high pass filter with lower noise than the lowest noise >>> references and the capacitor is the problem. >>> >>> In Linear Technology Application Note 124, Jim Williams discusses the >>> problems with electrolytic capacitors for this type of application. I >>> have read that you *can* get away with aluminum electrolytics if you >>> grade them for low leakage and low noise. The dielectric absorption >>> is also a problem unless you can wait hours for best performance. >>> >>> What about the alternative of buffering the signal with a low noise >>> low input bias current operational amplifier so that a large film >>> capacitor can be used instead? Is the low frequency noise of a good >>> operational amplifier still too much? What about a chopper stabilized >>> amplifier without suitable output filter? > ___ > 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] Adafruit Ultimate GPS timing message arrival times
> On Aug 1, 2016, at 9:33 AM, Chris Albertson wrote: > > > > In fact that would be a good experiment: Put two clocks up on a large > computer monitor and make one always tick some random number of > milliseconds away from system time and the other always thick on the > system time. Then you click on the one you think is correct. Can you > do better than a 50/50 guess. Keep incl=reasing the error until the > guesses are about 90% correct. I bet you find you eyes are really > bad. You ears are a little better and you might notice 40 mS by > listening to the "tick" sound > I’ve done something akin to this with my Crazy Clock movements. The Vetinari clock works by stealing 100 ms from a fraction of the ticks until it’s gathered up enough to do a “double tick.” I wrote the firmware and I can’t tell which seconds are 100 ms off. There’s also the “Whacky” firmware. It ticks on a random tenth of a second within each second. In practice, it’s far more subtle than I thought it would be. It’s only really obvious when it picks values far apart from their neighbors. ___ 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] Effect of EFC noise on phase noise
Are the EFC inputs all directly DC coupled to the varactor diodes making them high DC impedance? I always thought they should bring the varactor or EFC ground out as a separate pin but I assume that since they do not, ground noise at least within the oscillator does not limit performance. In the past when I have had low frequency ground noise, I have either used an instrumentation amplifier at the load or used a high impedance current source with a load resistor to ground at the load. But I have difficulty imagining either being used to drive an EFC input because close proximity of the driving circuit allows it to use the oscillator ground as a single point ground. I wonder if there is anything to be learned by studying how the old varactor based (parametric) operational amplifiers were used. On Mon, 1 Aug 2016 16:32:35 -0400, you wrote: >Hi > >If you wire up all the possible circuits and check them all out the >answer is that big C / small R wins. Big R gets you into resistor noise issues >and stray pickup. > >Bob > >> On Aug 1, 2016, at 4:16 PM, David wrote: >> >> This duplicates the problems encountered when trying to quantify low >> frequency noise from a voltage reference; it is difficult to make an >> low frequency high pass filter with lower noise than the lowest noise >> references and the capacitor is the problem. >> >> In Linear Technology Application Note 124, Jim Williams discusses the >> problems with electrolytic capacitors for this type of application. I >> have read that you *can* get away with aluminum electrolytics if you >> grade them for low leakage and low noise. The dielectric absorption >> is also a problem unless you can wait hours for best performance. >> >> What about the alternative of buffering the signal with a low noise >> low input bias current operational amplifier so that a large film >> capacitor can be used instead? Is the low frequency noise of a good >> operational amplifier still too much? What about a chopper stabilized >> amplifier without suitable output filter? ___ 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] Effect of EFC noise on phase noise
Am 01.08.2016 um 22:16 schrieb David: This duplicates the problems encountered when trying to quantify low frequency noise from a voltage reference; it is difficult to make an low frequency high pass filter with lower noise than the lowest noise references and the capacitor is the problem. I beg to differ. Voltage references are not that wonderful. Bandgaps live from amplifying small voltage differences and stable Zener references at 6 to 7 Volts are plagued by avalanche noise. And that includes the LT6655 band gap. WRT short term stability all of these are eclipsed by 2.7 / 3.3 volt zeners and by LEDs. Even the LT6655 gains a lot of noise performance from an active filter with AD797 / ADA4898 op amps and even resistors and 6V/1000uF Nipon Chemi SMD electrolytics. I have made some absolute noise voltage measurements: < https://www.flickr.com/photos/137684711@N07/albums/72157662535945536 > LEDs and Zeners are measured with bias from a 1 or 2k wire resistor and a 14V NiMH battery. I find the HLMP6000 LED really impressive and the LT3042 regulator. The preamp is 20 ADA4898 op amps in parallel ( i.e. 220pV/sqrtHz), the 0 dB line is 1 nV/sqrt Hz. Everything was fed from batteries in a box in box in a box and then after +80 dB passed to an 89441A vector signal analyzer. The input capacitor of the preamp is 20 times 10uF WIMA foil, that is not enough for the low frequency corner as we do not see the real 1/f noise below 20 Hz. What we see looks more like GR noise, spectrum-wise, and it is really the insufficient shorting of the 10K bias resistor through the input source and coupling cap. I have bought some wet slug tantals as proposed by Jim Williams (see below), 1 uF bring the right 1/f behaviour but at very substantial cost :-(At least for small input voltages alu electrolytics do not seem to make a difference. I did not test large voltages. I'm working on a new amplifier based on IF3602 or BF862 FETs that can use 10u foil only. When it's done I'll repeat these measurements. In Linear Technology Application Note 124, Jim Williams discusses the problems with electrolytic capacitors for this type of application. I have read that you *can* get away with aluminum electrolytics if you grade them for low leakage and low noise. The dielectric absorption is also a problem unless you can wait hours for best performance. JW has the added handicap that he wants to keep the the long term and absolute stability of his reference and so cannot afford any voltage drop on a series R. We do not share that problem on an EFC line because the C stands for control and if the voltage there does never change for some other reason we have probably made a bad decision with regard to loop gain. And large resistors may feature more noise voltage, but that increases only with the root of the resistance. The filter corner drops in a linear way, so a large resistor may really help. The tiny noise voltage of a reasonable resistor must be seen anyway in the context of say, a 10811A that tunes +- 1 Hz for 10 Volts on the EFC. regards, Gerhard ___ 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] Effect of EFC noise on phase noise
Yep, it supports the big C (padded out with increasingly smaller caps) in general wins. For two low pass filters, one with say 100nF and one with 10nF, same fc, the 100nF filter will have 10 times less noise power, or sqrt(10) less rms noise. Near DC is another story. On Mon, Aug 1, 2016 at 5:10 PM, Bob Camp wrote: > HI > > Broadband is not where you run into the trouble on any of these circuits. > It’s > always what happens within a decade or two past cutoff or inside the pass > band. > > Bob > > > On Aug 1, 2016, at 4:50 PM, Scott Stobbe > wrote: > > > > The broadband thermal noise at a circuit point with a cap is always kT/c > > > > On Monday, 1 August 2016, Bob Camp wrote: > > > >> Hi > >> > >> If you wire up all the possible circuits and check them all out … the > >> answer is that big C / small R wins. Big R gets you into resistor noise > >> issues > >> and stray pickup. > >> > >> Bob > >> > >>> On Aug 1, 2016, at 4:16 PM, David > > >> wrote: > >>> > >>> This duplicates the problems encountered when trying to quantify low > >>> frequency noise from a voltage reference; it is difficult to make an > >>> low frequency high pass filter with lower noise than the lowest noise > >>> references and the capacitor is the problem. > >>> > >>> In Linear Technology Application Note 124, Jim Williams discusses the > >>> problems with electrolytic capacitors for this type of application. I > >>> have read that you *can* get away with aluminum electrolytics if you > >>> grade them for low leakage and low noise. The dielectric absorption > >>> is also a problem unless you can wait hours for best performance. > >>> > >>> What about the alternative of buffering the signal with a low noise > >>> low input bias current operational amplifier so that a large film > >>> capacitor can be used instead? Is the low frequency noise of a good > >>> operational amplifier still too much? What about a chopper stabilized > >>> amplifier without suitable output filter? > >>> > >>> On Mon, 1 Aug 2016 11:46:51 -0400, you wrote: > >>> > Hi > > > >>> .. until you discover that you picked the *wrong* capacitor > manufacturer > >> and you have > more noise from leakage in the cap than you did to start out with :) > >> In general “big C and > small R” is the better solution than “big R and small C”. > > The pesky part is that with electrolytic caps, the whole “noise > >> current” thing changes as > the voltage moves around. You go to measure things and by the time the > >> gear is set up, > the noise has dropped. Turn it all off, come back the next day and > it’s > >> noisy again. > > An even more subtle issue can be capacitor temperature coefficient on > >> really long Tau filters. If C > changes (due to temperature fluxuations) faster than the settling time > >> of the filter, you get noise. Charge > is the same so delta C gives delta V. > > I *wish* I could tell you that was all purely theoretical. > >> Unfortunately it’s based on empirical data > collected in the “how could I be so stupid” fashion. > > Bob > > > On Aug 1, 2016, at 11:21 AM, KA2WEU--- via time-nuts < > >> time-nuts@febo.com > wrote: > > > > A good filter in the cable is highly recommended, 5 KOhm & 1000 uF > >> cleans > > many things > >>> ___ > >>> 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 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 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] Effect of EFC noise on phase noise
With my filter , I had good success and 5 K is not too high , Ulrich Sent from my iPhone > On Aug 1, 2016, at 11:46 AM, Bob Camp wrote: > > Hi > > ….. until you discover that you picked the *wrong* capacitor manufacturer and > you have > more noise from leakage in the cap than you did to start out with :) In > general “big C and > small R” is the better solution than “big R and small C”. > > The pesky part is that with electrolytic caps, the whole “noise current” > thing changes as > the voltage moves around. You go to measure things and by the time the gear > is set up, > the noise has dropped. Turn it all off, come back the next day and it’s noisy > again. > > An even more subtle issue can be capacitor temperature coefficient on really > long Tau filters. If C > changes (due to temperature fluxuations) faster than the settling time of the > filter, you get noise. Charge > is the same so delta C gives delta V. > > I *wish* I could tell you that was all purely theoretical. Unfortunately it’s > based on empirical data > collected in the “how could I be so stupid” fashion. > > Bob > >> On Aug 1, 2016, at 11:21 AM, KA2WEU--- via time-nuts >> wrote: >> >> A good filter in the cable is highly recommended, 5 KOhm & 1000 uF cleans >> many things >> >> >> In a message dated 8/1/2016 11:12:51 A.M. Eastern Daylight Time, >> kb...@n1k.org writes: >> >> Hi >> >> It’s just very standard FM modulation math. The only gotcha is the >> (often unknown) bandwidth of the EFC port. Even on a precision >> OCXO, it might be <10 Hz, it might be over a KHz …. The trap many >> fall into is the “small angle” restriction. You can get into modulation >> indexes that will get the second and third order terms contributing. >> It’s more common to see on vibration, but it can happen on a noisy >> EFC. >> >> Bob >> >> >>> On Aug 1, 2016, at 9:46 AM, Attila Kinali wrote: >>> >>> Moin, >>> >>> I need some formulas that relate EFC noise to the (added) phase noise of >>> an OCXO. It shouldn't be too difficult to come up with something. But >>> before I make some stupid mistakes, i wanted to ask whether someone >>> has already done this or has any references to papers? My google-foo >>> was not strong enough to find something. >>> >>> Attila Kinali >>> >>> -- >>> It is upon moral qualities that a society is ultimately founded. All >>> the prosperity and technological sophistication in the world is of no >>> use without that foundation. >>> -- Miss Matheson, The Diamond Age, Neil Stephenson >>> ___ >>> 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 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] Effect of EFC noise on phase noise
HI Broadband is not where you run into the trouble on any of these circuits. It’s always what happens within a decade or two past cutoff or inside the pass band. Bob > On Aug 1, 2016, at 4:50 PM, Scott Stobbe wrote: > > The broadband thermal noise at a circuit point with a cap is always kT/c > > On Monday, 1 August 2016, Bob Camp wrote: > >> Hi >> >> If you wire up all the possible circuits and check them all out … the >> answer is that big C / small R wins. Big R gets you into resistor noise >> issues >> and stray pickup. >> >> Bob >> >>> On Aug 1, 2016, at 4:16 PM, David > >> wrote: >>> >>> This duplicates the problems encountered when trying to quantify low >>> frequency noise from a voltage reference; it is difficult to make an >>> low frequency high pass filter with lower noise than the lowest noise >>> references and the capacitor is the problem. >>> >>> In Linear Technology Application Note 124, Jim Williams discusses the >>> problems with electrolytic capacitors for this type of application. I >>> have read that you *can* get away with aluminum electrolytics if you >>> grade them for low leakage and low noise. The dielectric absorption >>> is also a problem unless you can wait hours for best performance. >>> >>> What about the alternative of buffering the signal with a low noise >>> low input bias current operational amplifier so that a large film >>> capacitor can be used instead? Is the low frequency noise of a good >>> operational amplifier still too much? What about a chopper stabilized >>> amplifier without suitable output filter? >>> >>> On Mon, 1 Aug 2016 11:46:51 -0400, you wrote: >>> Hi >>> .. until you discover that you picked the *wrong* capacitor manufacturer >> and you have more noise from leakage in the cap than you did to start out with :) >> In general “big C and small R” is the better solution than “big R and small C”. The pesky part is that with electrolytic caps, the whole “noise >> current” thing changes as the voltage moves around. You go to measure things and by the time the >> gear is set up, the noise has dropped. Turn it all off, come back the next day and it’s >> noisy again. An even more subtle issue can be capacitor temperature coefficient on >> really long Tau filters. If C changes (due to temperature fluxuations) faster than the settling time >> of the filter, you get noise. Charge is the same so delta C gives delta V. I *wish* I could tell you that was all purely theoretical. >> Unfortunately it’s based on empirical data collected in the “how could I be so stupid” fashion. Bob > On Aug 1, 2016, at 11:21 AM, KA2WEU--- via time-nuts < >> time-nuts@febo.com > wrote: > > A good filter in the cable is highly recommended, 5 KOhm & 1000 uF >> cleans > many things >>> ___ >>> 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 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] Q/noise of Earth as an oscillator
A bit short on the phone... Both the ECI and ECEF frames are rotating at sidreal rate. The earth rate is (a small) part of the navigation equations. Thus its needed in inertial nav. Glenn, look at the performance of the big land RLGs - NZ and German that were linked last week. How much better are those compared to your (also extremely good) sub gyros.-- Björn Sent from my smartphone. Original message From: Tom Van Baak Date: 01/08/2016 20:01 (GMT+01:00) To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Q/noise of Earth as an oscillator Hi Glenn, Your 15.04 number rings a bell [1]. The conventional solar day is simply 86400 seconds (24 hours). So each hour is 15 degrees, exactly. But the actual (sidereal) earth rotation rate is about 86164 SI seconds (23h 56m 4.091s). So each hour is 15.0411 degrees. Someone who understands celestial mechanics or an ex-Navy person with sextant skills could explain better, but I bet that's where your 15.04 number comes from. /tvb [1] http://www.navy.mil/navydata/questions/bells.html ;-) - Original Message - From: "Glenn Little WB4UIV" To: "Tom Van Baak" ; "Discussion of precise time and frequency measurement" Sent: Monday, August 01, 2016 10:38 AM Subject: Re: [time-nuts] Q/noise of Earth as an oscillator In navigation we used the earth rate of 15.04 degrees per hour. This was treated as a 'constant' even though it varied with wind, waves on the ocean and other things affecting the instantaneous rotational speed of the earth. How does this factor into leap seconds, or, does it? We accept that the day is 24 hours long, this would be for a earth rotational speed of 15.0 degrees per hour. I am not a mathematician, but, I dis do electronic navigation on submarines. 73 Glenn WB4UIV On 8/1/2016 10:54 AM, Tom Van Baak wrote: > Hi Jim. > >> You said: "you need energy; you need energy loss; you need cycles over which >> that loss repeatedly occurs." >> With regard to the earth, where is the first one? > > By first one, do you mean where does the initial energy come from? > > For a pendulum clock, you supply energy with a lift or a push. For a lift to > the side, E = mgh, where h is the height above the base. For a push from > center, E = 1/2 mv^2. Either way, it takes all the potential or kinetic E you > provide and starts making time from there. > > For a rotating clock, you just give it a twist. In this case, E = 1/2 Iw^2, > where I is the moment of inertia and w (omega) is angular velocity. For earth > the total E is 2.1e29 J. That's the energy number you want, yes? > >> Sure it was there at the start when the solar system formed, but where is it >> now? > > I don't have data on where the initial swirl of solar system mass came from, > or how much of that rotational energy went into our planet and its pesky > moon, or Who or what gave that initial twist. The Q is pretty high so I > assume you could work backwards, but I leave that to astronomers and > cosmologists. I believe the 2 ms/day / century estimate we use is one such > measurement. > > For more on earth rotation rate, UTC and leap seconds see > https://www.ucolick.org/~sla/leapsecs/dutc.html > > Surely in the literature there is a pile of information or speculation > regarding all the rotational energy in the universe. It seems a common theme > everywhere you look; maybe it was as much Big Twist as Big Bang? Perhaps in > your Pulsar research you've run across some papers you could share. Off-list > is ok, unless you think it has general time-nuts appeal. We're running the > risk of spinning off-topic already. > > Thanks, > /tvb > > - Original Message - > From: "Jim Palfreyman" > To: "Discussion of precise time and frequency measurement" > > Sent: Sunday, July 31, 2016 7:34 PM > Subject: Re: [time-nuts] Q/noise of Earth as an oscillator > > > Hi Tom, > > You said: "you need energy; you need energy loss; you need cycles over > which that loss repeatedly occurs." > > With regard to the earth, where is the first one? Sure it was there at the > start when the solar system formed, but where is it now? > > Jim > > > On 1 August 2016 at 12:16, Tom Van Baak wrote: > >> Hal: >>> Is there a term other than Q that is used to describe the rate of energy >> loss >>> for things that aren't oscillators? >> >> Jim: >>> cooling (as in hot things) >>> discharge (as in capacitors and batteries) >>> leakage (as in pressure vessels) >>> loss >> >> Scott: >>> An irreversible process would be a better description versus energy loss. >>> Like joule heating (resistance, friction). >> >> Notice that these are all energy losses over time; gradual processes with >> perhaps an exponential time constant, but without cycles or periods. We >> know not to apply Q in these scenarios. >> >> But when you have an oscillator, or a resonator, or (as I suggest) a >> "rotator", it seems to make sense to use Q to describe the normalized
Re: [time-nuts] Effect of EFC noise on phase noise
The broadband thermal noise at a circuit point with a cap is always kT/c On Monday, 1 August 2016, Bob Camp wrote: > Hi > > If you wire up all the possible circuits and check them all out … the > answer is that big C / small R wins. Big R gets you into resistor noise > issues > and stray pickup. > > Bob > > > On Aug 1, 2016, at 4:16 PM, David > > wrote: > > > > This duplicates the problems encountered when trying to quantify low > > frequency noise from a voltage reference; it is difficult to make an > > low frequency high pass filter with lower noise than the lowest noise > > references and the capacitor is the problem. > > > > In Linear Technology Application Note 124, Jim Williams discusses the > > problems with electrolytic capacitors for this type of application. I > > have read that you *can* get away with aluminum electrolytics if you > > grade them for low leakage and low noise. The dielectric absorption > > is also a problem unless you can wait hours for best performance. > > > > What about the alternative of buffering the signal with a low noise > > low input bias current operational amplifier so that a large film > > capacitor can be used instead? Is the low frequency noise of a good > > operational amplifier still too much? What about a chopper stabilized > > amplifier without suitable output filter? > > > > On Mon, 1 Aug 2016 11:46:51 -0400, you wrote: > > > >> Hi > >> > >> > > .. until you discover that you picked the *wrong* capacitor manufacturer > and you have > >> more noise from leakage in the cap than you did to start out with :) > In general “big C and > >> small R” is the better solution than “big R and small C”. > >> > >> The pesky part is that with electrolytic caps, the whole “noise > current” thing changes as > >> the voltage moves around. You go to measure things and by the time the > gear is set up, > >> the noise has dropped. Turn it all off, come back the next day and it’s > noisy again. > >> > >> An even more subtle issue can be capacitor temperature coefficient on > really long Tau filters. If C > >> changes (due to temperature fluxuations) faster than the settling time > of the filter, you get noise. Charge > >> is the same so delta C gives delta V. > >> > >> I *wish* I could tell you that was all purely theoretical. > Unfortunately it’s based on empirical data > >> collected in the “how could I be so stupid” fashion. > >> > >> Bob > >> > >>> On Aug 1, 2016, at 11:21 AM, KA2WEU--- via time-nuts < > time-nuts@febo.com > wrote: > >>> > >>> A good filter in the cable is highly recommended, 5 KOhm & 1000 uF > cleans > >>> many things > > ___ > > 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 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] Effect of EFC noise on phase noise
Hi If you are in the region that a low noise reference will apply to a low deviation precision standard, you are deep into “small angle” territory. The higher order stuff simply does not apply. Rotate the spectrum by 1/f (FM -> PM) and calculate the level at 1 Hz …..end of story. If when you are done you have phase noise that is above -60 dbc in a 1Hz bandwidth above 1 Hz, go back and look at the small angle assumption. 60 db is still well inside the safe region so you still are likely to come back with “no problem”. Bob > On Aug 1, 2016, at 3:01 PM, jimlux wrote: > > On 8/1/16 8:18 AM, Attila Kinali wrote: >> On Mon, 01 Aug 2016 14:36:28 + >> "Poul-Henning Kamp" wrote: >> I need some formulas that relate EFC noise to the (added) phase noise of an OCXO. It shouldn't be too difficult to come up with something. But before I make some stupid mistakes, i wanted to ask whether someone has already done this or has any references to papers? My google-foo was not strong enough to find something. >>> >>> Isn't that just FM modulation ? >> >> Yes, it is. The problem is not the theory. The problem is to calculate >> the correct values. I know i can figure it out, but if there are ready >> to use formulas that are known to be correct, I rather use those. > > Rather than deriving Bessel functions from first principles? > > It's an interesting problem.. What you're really looking for is the spectrum > of the output with the FM modulation process acting on the spectrum of the > modulation. As noted by others, you need to know the bandwidth (and then > assume that it's "flat" within that bandwidth). > > FM modulation isn't linear: that is, if I feed a 10 Hz and a 15 Hz signal > into a FM modulator, the spectrum I get out is not just the superposition of > the spectrum with just 10 Hz and just 15 Hz. > > The spectrum of a single tone modulation is easy: it's the Bessel function of > the appropriate order with the appropriate scale factors. > > Somewhere I've got a derivation of this: I was more concerned with phase > modulation (heartbeat motion and respiration motion both modulate the > reflected radar signal, so the spectrum you see is a combination of the two): > it isn't pretty in an analytical sense. I wound up just doing numerical > simulation: you don't have to worry about whether you are violating the small > angle approximation, etc. > > A couple of papers from the 60s that seem to be on point... > > > http://www.sciencedirect.com/science/article/pii/S0019995866800062 > > http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=5245193 > > The Medhurst paper seems to be the one you want. > "When the frequency modulation may be simulated by a band of > random noise (as in multiplex telephony carrying large numbers of > channels), the spectra of the distortion products can, in principle, > be described by simple algebraic functions of the characteristics > (i.e. the minimum and maximum frequencies and the r.m.s. frequency > deviaion) of the modulating noise band." > > > I note that "simple algebraic functions" take up the better part of a page. > Simulation looks more and more attractive. > > > > > > >> >> Attila Kinali >> > > ___ > 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] Effect of EFC noise on phase noise
Hi If you wire up all the possible circuits and check them all out … the answer is that big C / small R wins. Big R gets you into resistor noise issues and stray pickup. Bob > On Aug 1, 2016, at 4:16 PM, David wrote: > > This duplicates the problems encountered when trying to quantify low > frequency noise from a voltage reference; it is difficult to make an > low frequency high pass filter with lower noise than the lowest noise > references and the capacitor is the problem. > > In Linear Technology Application Note 124, Jim Williams discusses the > problems with electrolytic capacitors for this type of application. I > have read that you *can* get away with aluminum electrolytics if you > grade them for low leakage and low noise. The dielectric absorption > is also a problem unless you can wait hours for best performance. > > What about the alternative of buffering the signal with a low noise > low input bias current operational amplifier so that a large film > capacitor can be used instead? Is the low frequency noise of a good > operational amplifier still too much? What about a chopper stabilized > amplifier without suitable output filter? > > On Mon, 1 Aug 2016 11:46:51 -0400, you wrote: > >> Hi >> >> > .. until you discover that you picked the *wrong* capacitor manufacturer and > you have >> more noise from leakage in the cap than you did to start out with :) In >> general big C and >> small R is the better solution than big R and small C. >> >> The pesky part is that with electrolytic caps, the whole noise current >> thing changes as >> the voltage moves around. You go to measure things and by the time the gear >> is set up, >> the noise has dropped. Turn it all off, come back the next day and its >> noisy again. >> >> An even more subtle issue can be capacitor temperature coefficient on really >> long Tau filters. If C >> changes (due to temperature fluxuations) faster than the settling time of >> the filter, you get noise. Charge >> is the same so delta C gives delta V. >> >> I *wish* I could tell you that was all purely theoretical. Unfortunately >> its based on empirical data >> collected in the how could I be so stupid fashion. >> >> Bob >> >>> On Aug 1, 2016, at 11:21 AM, KA2WEU--- via time-nuts >>> wrote: >>> >>> A good filter in the cable is highly recommended, 5 KOhm & 1000 uF cleans >>> many things > ___ > 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] Effect of EFC noise on phase noise
This duplicates the problems encountered when trying to quantify low frequency noise from a voltage reference; it is difficult to make an low frequency high pass filter with lower noise than the lowest noise references and the capacitor is the problem. In Linear Technology Application Note 124, Jim Williams discusses the problems with electrolytic capacitors for this type of application. I have read that you *can* get away with aluminum electrolytics if you grade them for low leakage and low noise. The dielectric absorption is also a problem unless you can wait hours for best performance. What about the alternative of buffering the signal with a low noise low input bias current operational amplifier so that a large film capacitor can be used instead? Is the low frequency noise of a good operational amplifier still too much? What about a chopper stabilized amplifier without suitable output filter? On Mon, 1 Aug 2016 11:46:51 -0400, you wrote: >Hi > > .. until you discover that you picked the *wrong* capacitor manufacturer and >you have >more noise from leakage in the cap than you did to start out with :) In >general big C and >small R is the better solution than big R and small C. > >The pesky part is that with electrolytic caps, the whole noise current thing >changes as >the voltage moves around. You go to measure things and by the time the gear is >set up, >the noise has dropped. Turn it all off, come back the next day and its noisy >again. > >An even more subtle issue can be capacitor temperature coefficient on really >long Tau filters. If C >changes (due to temperature fluxuations) faster than the settling time of the >filter, you get noise. Charge >is the same so delta C gives delta V. > >I *wish* I could tell you that was all purely theoretical. Unfortunately its >based on empirical data >collected in the how could I be so stupid fashion. > >Bob > >> On Aug 1, 2016, at 11:21 AM, KA2WEU--- via time-nuts >> wrote: >> >> A good filter in the cable is highly recommended, 5 KOhm & 1000 uF cleans >> many things ___ 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] Effect of EFC noise on phase noise
I don't have the answer of the top of my head, but phase noise of VCOs and PLLs is well documented. Perhaps "loop filter noise vco" or the like may help. On Mon, Aug 1, 2016 at 11:18 AM, Attila Kinali wrote: > On Mon, 01 Aug 2016 14:36:28 + > "Poul-Henning Kamp" wrote: > > > >I need some formulas that relate EFC noise to the (added) phase noise of > > >an OCXO. It shouldn't be too difficult to come up with something. But > > >before I make some stupid mistakes, i wanted to ask whether someone > > >has already done this or has any references to papers? My google-foo > > >was not strong enough to find something. > > > > Isn't that just FM modulation ? > > Yes, it is. The problem is not the theory. The problem is to calculate > the correct values. I know i can figure it out, but if there are ready > to use formulas that are known to be correct, I rather use those. > > Attila Kinali > > -- > It is upon moral qualities that a society is ultimately founded. All > the prosperity and technological sophistication in the world is of no > use without that foundation. > -- Miss Matheson, The Diamond Age, Neil Stephenson > ___ > 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] Adafruit Ultimate GPS timing message arrival times
Yo Mark! On Sat, 30 Jul 2016 20:14:02 + Mark Sims wrote: > A couple of people have asked about the poor message arrival time > performance of the popular Adafruit Ultimate GPS receiver. I have several months of Adafruit graphs. I also find that is is usually as accurate as you would expect. But often it just seems to have huge swings in Lat/Lon even while stationary. Here is are two 24 hour scatter plots: https://pi2.rellim.com/pi2.png https://pi2.rellim.com/pi2-2.png RGDS GARY --- Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703 g...@rellim.com Tel:+1 541 382 8588 pgpJmQaMv4tGe.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] Effect of EFC noise on phase noise
On 8/1/16 8:18 AM, Attila Kinali wrote: On Mon, 01 Aug 2016 14:36:28 + "Poul-Henning Kamp" wrote: I need some formulas that relate EFC noise to the (added) phase noise of an OCXO. It shouldn't be too difficult to come up with something. But before I make some stupid mistakes, i wanted to ask whether someone has already done this or has any references to papers? My google-foo was not strong enough to find something. Isn't that just FM modulation ? Yes, it is. The problem is not the theory. The problem is to calculate the correct values. I know i can figure it out, but if there are ready to use formulas that are known to be correct, I rather use those. Rather than deriving Bessel functions from first principles? It's an interesting problem.. What you're really looking for is the spectrum of the output with the FM modulation process acting on the spectrum of the modulation. As noted by others, you need to know the bandwidth (and then assume that it's "flat" within that bandwidth). FM modulation isn't linear: that is, if I feed a 10 Hz and a 15 Hz signal into a FM modulator, the spectrum I get out is not just the superposition of the spectrum with just 10 Hz and just 15 Hz. The spectrum of a single tone modulation is easy: it's the Bessel function of the appropriate order with the appropriate scale factors. Somewhere I've got a derivation of this: I was more concerned with phase modulation (heartbeat motion and respiration motion both modulate the reflected radar signal, so the spectrum you see is a combination of the two): it isn't pretty in an analytical sense. I wound up just doing numerical simulation: you don't have to worry about whether you are violating the small angle approximation, etc. A couple of papers from the 60s that seem to be on point... http://www.sciencedirect.com/science/article/pii/S0019995866800062 http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=5245193 The Medhurst paper seems to be the one you want. "When the frequency modulation may be simulated by a band of random noise (as in multiplex telephony carrying large numbers of channels), the spectra of the distortion products can, in principle, be described by simple algebraic functions of the characteristics (i.e. the minimum and maximum frequencies and the r.m.s. frequency deviaion) of the modulating noise band." I note that "simple algebraic functions" take up the better part of a page. Simulation looks more and more attractive. Attila Kinali ___ 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] Q/noise of Earth as an oscillator
glennmaill...@bellsouth.net said: > In navigation we used the earth rate of 15.04 degrees per hour. This was > treated as a 'constant' even though it varied with wind, waves on the ocean > and other things affecting the instantaneous rotational speed of the earth. Were the wind and waves and whatever significant? Measurable? > How does this factor into leap seconds, or, does it? Leap seconds are necessary to correct for the unpredictable things like waves and earthquakes and ice caps melting. There is also tidal friction which is slowing down the rate of rotation. So even if the wind and friends were insignificant we would need to adjust the clocks occasionally. > We accept that the day is 24 hours long, this would be for a earth > rotational speed of 15.0 degrees per hour. The 0.04 is the difference between solar (sun) and sidereal (stars) time. During a year, the earth goes around the sun. If your clock runs on solar time but you are looking at the stars, that adds one more rotation per year. That's 360/365 degrees per day or 0.04 degrees per hour. -- These are my opinions. I hate spam. ___ 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] Adafruit Ultimate GPS timing message arrival times
HI You very much are not *done* when you get your point at a million seconds. That’s just where you get to *start* …. Since you are talking about nearly two weeks per sample, there are a *lot* of things that could happen. If your loop needs ten samples to do much with, it will be 4 months before anything at all happens. In that period, you need to wonder if the power will stay on for the whole time …. (thunderstorms in the area at the moment …) Even if you back off to “I only need 1 ppm”, you still have a really slow process. Bob > On Aug 1, 2016, at 1:35 PM, Hal Murray wrote: > > > kb...@n1k.org said: >> If I start with a serial string that is good to 10ms and my goal is 10 ppb, >> I’m waiting for a million seconds per sample. > > That also assumes that the temperature isn't changing while you are > collecting the data. > > > > -- > These are my opinions. I hate spam. > > > > ___ > 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] Q/noise of Earth as an oscillator
Hi Glenn, Your 15.04 number rings a bell [1]. The conventional solar day is simply 86400 seconds (24 hours). So each hour is 15 degrees, exactly. But the actual (sidereal) earth rotation rate is about 86164 SI seconds (23h 56m 4.091s). So each hour is 15.0411 degrees. Someone who understands celestial mechanics or an ex-Navy person with sextant skills could explain better, but I bet that's where your 15.04 number comes from. /tvb [1] http://www.navy.mil/navydata/questions/bells.html ;-) - Original Message - From: "Glenn Little WB4UIV" To: "Tom Van Baak" ; "Discussion of precise time and frequency measurement" Sent: Monday, August 01, 2016 10:38 AM Subject: Re: [time-nuts] Q/noise of Earth as an oscillator In navigation we used the earth rate of 15.04 degrees per hour. This was treated as a 'constant' even though it varied with wind, waves on the ocean and other things affecting the instantaneous rotational speed of the earth. How does this factor into leap seconds, or, does it? We accept that the day is 24 hours long, this would be for a earth rotational speed of 15.0 degrees per hour. I am not a mathematician, but, I dis do electronic navigation on submarines. 73 Glenn WB4UIV On 8/1/2016 10:54 AM, Tom Van Baak wrote: > Hi Jim. > >> You said: "you need energy; you need energy loss; you need cycles over which >> that loss repeatedly occurs." >> With regard to the earth, where is the first one? > > By first one, do you mean where does the initial energy come from? > > For a pendulum clock, you supply energy with a lift or a push. For a lift to > the side, E = mgh, where h is the height above the base. For a push from > center, E = 1/2 mv^2. Either way, it takes all the potential or kinetic E you > provide and starts making time from there. > > For a rotating clock, you just give it a twist. In this case, E = 1/2 Iw^2, > where I is the moment of inertia and w (omega) is angular velocity. For earth > the total E is 2.1e29 J. That's the energy number you want, yes? > >> Sure it was there at the start when the solar system formed, but where is it >> now? > > I don't have data on where the initial swirl of solar system mass came from, > or how much of that rotational energy went into our planet and its pesky > moon, or Who or what gave that initial twist. The Q is pretty high so I > assume you could work backwards, but I leave that to astronomers and > cosmologists. I believe the 2 ms/day / century estimate we use is one such > measurement. > > For more on earth rotation rate, UTC and leap seconds see > https://www.ucolick.org/~sla/leapsecs/dutc.html > > Surely in the literature there is a pile of information or speculation > regarding all the rotational energy in the universe. It seems a common theme > everywhere you look; maybe it was as much Big Twist as Big Bang? Perhaps in > your Pulsar research you've run across some papers you could share. Off-list > is ok, unless you think it has general time-nuts appeal. We're running the > risk of spinning off-topic already. > > Thanks, > /tvb > > - Original Message - > From: "Jim Palfreyman" > To: "Discussion of precise time and frequency measurement" > > Sent: Sunday, July 31, 2016 7:34 PM > Subject: Re: [time-nuts] Q/noise of Earth as an oscillator > > > Hi Tom, > > You said: "you need energy; you need energy loss; you need cycles over > which that loss repeatedly occurs." > > With regard to the earth, where is the first one? Sure it was there at the > start when the solar system formed, but where is it now? > > Jim > > > On 1 August 2016 at 12:16, Tom Van Baak wrote: > >> Hal: >>> Is there a term other than Q that is used to describe the rate of energy >> loss >>> for things that aren't oscillators? >> >> Jim: >>> cooling (as in hot things) >>> discharge (as in capacitors and batteries) >>> leakage (as in pressure vessels) >>> loss >> >> Scott: >>> An irreversible process would be a better description versus energy loss. >>> Like joule heating (resistance, friction). >> >> Notice that these are all energy losses over time; gradual processes with >> perhaps an exponential time constant, but without cycles or periods. We >> know not to apply Q in these scenarios. >> >> But when you have an oscillator, or a resonator, or (as I suggest) a >> "rotator", it seems to make sense to use Q to describe the normalized rate >> of decay. So three keys to Q: you need energy; you need energy loss; you >> need cycles over which that loss repeatedly occurs. >> >> We use units of time (for example, SI seconds) when we describe a rate. >> But here's why Q is unitless -- you normalize the energy (using E / dE) >> *and* you also normalize the time (by cycle). No Joules. No seconds. So >> having period is fundamental to Q. It's this unitless character of Q (in >> both energy and time) that makes it portable from one branch of science to >> another. And if you measure in radians you can even get rid of the 2*pi >> factor ;-) >>
Re: [time-nuts] Q/noise of Earth as an oscillator
In navigation we used the earth rate of 15.04 degrees per hour.
This was treated as a 'constant' even though it varied with wind, waves
on the ocean and other things affecting the instantaneous rotational
speed of the earth.
How does this factor into leap seconds, or, does it?
We accept that the day is 24 hours long, this would be for a earth
rotational speed of 15.0 degrees per hour.
I am not a mathematician, but, I dis do electronic navigation on submarines.
73
Glenn
WB4UIV
On 8/1/2016 10:54 AM, Tom Van Baak wrote:
Hi Jim.
You said: "you need energy; you need energy loss; you need cycles over which that
loss repeatedly occurs."
With regard to the earth, where is the first one?
By first one, do you mean where does the initial energy come from?
For a pendulum clock, you supply energy with a lift or a push. For a lift to
the side, E = mgh, where h is the height above the base. For a push from
center, E = 1/2 mv^2. Either way, it takes all the potential or kinetic E you
provide and starts making time from there.
For a rotating clock, you just give it a twist. In this case, E = 1/2 Iw^2,
where I is the moment of inertia and w (omega) is angular velocity. For earth
the total E is 2.1e29 J. That's the energy number you want, yes?
Sure it was there at the start when the solar system formed, but where is it
now?
I don't have data on where the initial swirl of solar system mass came from, or
how much of that rotational energy went into our planet and its pesky moon, or
Who or what gave that initial twist. The Q is pretty high so I assume you could
work backwards, but I leave that to astronomers and cosmologists. I believe the
2 ms/day / century estimate we use is one such measurement.
For more on earth rotation rate, UTC and leap seconds see
https://www.ucolick.org/~sla/leapsecs/dutc.html
Surely in the literature there is a pile of information or speculation
regarding all the rotational energy in the universe. It seems a common theme
everywhere you look; maybe it was as much Big Twist as Big Bang? Perhaps in
your Pulsar research you've run across some papers you could share. Off-list is
ok, unless you think it has general time-nuts appeal. We're running the risk of
spinning off-topic already.
Thanks,
/tvb
- Original Message -
From: "Jim Palfreyman"
To: "Discussion of precise time and frequency measurement"
Sent: Sunday, July 31, 2016 7:34 PM
Subject: Re: [time-nuts] Q/noise of Earth as an oscillator
Hi Tom,
You said: "you need energy; you need energy loss; you need cycles over
which that loss repeatedly occurs."
With regard to the earth, where is the first one? Sure it was there at the
start when the solar system formed, but where is it now?
Jim
On 1 August 2016 at 12:16, Tom Van Baak wrote:
Hal:
Is there a term other than Q that is used to describe the rate of energy
loss
for things that aren't oscillators?
Jim:
cooling (as in hot things)
discharge (as in capacitors and batteries)
leakage (as in pressure vessels)
loss
Scott:
An irreversible process would be a better description versus energy loss.
Like joule heating (resistance, friction).
Notice that these are all energy losses over time; gradual processes with
perhaps an exponential time constant, but without cycles or periods. We
know not to apply Q in these scenarios.
But when you have an oscillator, or a resonator, or (as I suggest) a
"rotator", it seems to make sense to use Q to describe the normalized rate
of decay. So three keys to Q: you need energy; you need energy loss; you
need cycles over which that loss repeatedly occurs.
We use units of time (for example, SI seconds) when we describe a rate.
But here's why Q is unitless -- you normalize the energy (using E / dE)
*and* you also normalize the time (by cycle). No Joules. No seconds. So
having period is fundamental to Q. It's this unitless character of Q (in
both energy and time) that makes it portable from one branch of science to
another. And if you measure in radians you can even get rid of the 2*pi
factor ;-)
Without controversy, lots of articles define Q as 2*pi times {total
energy} / {energy lost per cycle}. To me, a slowly decaying spinning Earth
meets the three criteria. It appears to follow both the letter and the
spirit of Q.
Bob:
ummm…. Q is the general term of rate of energy loss and we just happen
to apply
it to oscillators in a very elegant fashion….
Oh, no. Now we have both quality factor and elegance factor!
/tvb
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- Original Message -
From: "Jim Palfreyman"
To: "Discussion of precise time
Re: [time-nuts] Adafruit Ultimate GPS timing message arrival times
From: Mark Sims Well, the whole point of the exercise is to see how well you can do if you DON'T have an internet connection, a 1PPS signal, or a stratum 1 time server available... only the humble messages coming from a 10 dollar GPS receiver. Try getting a net connection in the middle of the Gobi desert (where one user uses Lady Heather's time sync feature to keep their system clocks reasonably accurate). If you can put the receiver into a binary message mode, you can usually do better than NMEA (but, surprisingly, usually not by much). And by selecting a receiver that has known good / stable message timing you can do surprisingly well. Well, yes, but if you choose a GPS receiver wisely it also has PPS, even on some of the cheapest eBay units. Of course, what is best depends on what accuracy the user needs, and how much they are prepared to pay. 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] Adafruit Ultimate GPS timing message arrival times
kb...@n1k.org said: > If I start with a serial string that is good to 10ms and my goal is 10 ppb, > Iâm waiting for a million seconds per sample. That also assumes that the temperature isn't changing while you are collecting the data. -- These are my opinions. I hate spam. ___ 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] Adafruit Ultimate GPS timing message arrival times
Hi The issue with any of these approaches is how long it will take to converge. If I start with a pps that is good to 10 ns and my goal is 10 ns or 10 ppb, I’m there in a second. If I start with a serial string that is good to 10ms and my goal is 10 ppb, I’m waiting for a million seconds per sample. If I want to get an Rb to 1x10^-12, I need to wait for 10,000 seconds per sample with the pps. To do the same thing with the serial string is 10 billion seconds for each independent sample. The serial string is fine for an "eyeball clock". It’s not so fine for a GPSDO. Bob > On Aug 1, 2016, at 12:33 PM, Chris Albertson > wrote: > > You are right. NTP, even over a poor internet connection can > typically do better then the tens milliseconds we see with some NEMA > GPS'. > > But you eyes and human perfection is still even worse. You can't > notice 40mS of error. > > In fact that would be a good experiment: Put two clocks up on a large > computer monitor and make one always tick some random number of > milliseconds away from system time and the other always thick on the > system time. Then you click on the one you think is correct. Can you > do better than a 50/50 guess. Keep incl=reasing the error until the > guesses are about 90% correct. I bet you find you eyes are really > bad. You ears are a little better and you might notice 40 mS by > listening to the "tick" sound > > Another thought experiment is to show that the randomness of NMEA > jitter does not matter would be to try and build a GPSDO that uses > NMEA data. If you averaged over a long enough time it would work. > Might be a way to set a Rb oscillator? > > One reason NTP works so well even over poor Internet connections is > that it can use 5, 7 or even more other NTP servers to get the time > and all it needs is that a few of them are good. I typically use > five pool servers when I set up NTP > > > > > > On Mon, Aug 1, 2016 at 12:01 AM, Hal Murray wrote: >> >> david-tay...@blueyonder.co.uk said: >>> From your data and my own measurements, I feel that using the serial NMEA >>> stream would, today, be a last resort, as an Internet sync would be >>> considerably better. Would you agree with that? >> >> Depends on your internet connection and/or the specific GPS module you are >> using. >> >> I don't know of any good GPS modules that use NMEA. I do know of really >> crappy internet connections. Bufferbloat is the buzzword. >> >> >> >> -- >> These are my opinions. I hate spam. >> >> >> >> ___ >> 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. > > > > -- > > Chris Albertson > Redondo Beach, California > ___ > 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] Effect of EFC noise on phase noise
In message <20160801180601.3d27b82227616e847f340...@kinali.ch>, Attila Kinali w rites: >On Mon, 1 Aug 2016 11:21:10 -0400 >KA2WEU--- via time-nuts wrote: > >> A good filter in the cable is highly recommended, 5 KOhm & 1000 uF cleans >> many things > >Uhmm.. with 1mF in capacitors... don't you run into into microphonics problems? >Or all these capacitors supposed to be tantalum/aluminium caps? You certainly run into a separate source of temperature dependence, but of course only second order (change of temp). -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Adafruit Ultimate GPS timing message arrival times
As an exercise it might be fun to try to do the best you can with just NMEA. But practically speaking even my very $10, 8-channel motorola GPS receiver can output a PPS to about 50ns. Better then needed for NTP. You friend in the Gobi desert would be better off my $10 GPS That said, if you had a good local oscillator you could make a decent GPSDO using NMEA only with a VERY long time constant On Mon, Aug 1, 2016 at 9:23 AM, Mark Sims wrote: > Well, the whole point of the exercise is to see how well you can do if you > DON'T have an internet connection, a 1PPS signal, or a stratum 1 time server > available... only the humble messages coming from a 10 dollar GPS receiver. > Try getting a net connection in the middle of the Gobi desert (where one user > uses Lady Heather's time sync feature to keep their system clocks reasonably > accurate). > > > If you can put the receiver into a binary message mode, you can usually do > better than NMEA (but, surprisingly, usually not by much). And by selecting > a receiver that has known good / stable message timing you can do > surprisingly well. > > > -- > > >> I feel that using the serial NMEA stream would, today, be a last resort, as >> an Internet sync would be considerably better. Would you agree with that? > > > ___ > 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. -- Chris Albertson Redondo Beach, California ___ 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] Adafruit Ultimate GPS timing message arrival times
You are right. NTP, even over a poor internet connection can typically do better then the tens milliseconds we see with some NEMA GPS'. But you eyes and human perfection is still even worse. You can't notice 40mS of error. In fact that would be a good experiment: Put two clocks up on a large computer monitor and make one always tick some random number of milliseconds away from system time and the other always thick on the system time. Then you click on the one you think is correct. Can you do better than a 50/50 guess. Keep incl=reasing the error until the guesses are about 90% correct. I bet you find you eyes are really bad. You ears are a little better and you might notice 40 mS by listening to the "tick" sound Another thought experiment is to show that the randomness of NMEA jitter does not matter would be to try and build a GPSDO that uses NMEA data. If you averaged over a long enough time it would work. Might be a way to set a Rb oscillator? One reason NTP works so well even over poor Internet connections is that it can use 5, 7 or even more other NTP servers to get the time and all it needs is that a few of them are good. I typically use five pool servers when I set up NTP On Mon, Aug 1, 2016 at 12:01 AM, Hal Murray wrote: > > david-tay...@blueyonder.co.uk said: >> From your data and my own measurements, I feel that using the serial NMEA >> stream would, today, be a last resort, as an Internet sync would be >> considerably better. Would you agree with that? > > Depends on your internet connection and/or the specific GPS module you are > using. > > I don't know of any good GPS modules that use NMEA. I do know of really > crappy internet connections. Bufferbloat is the buzzword. > > > > -- > These are my opinions. I hate spam. > > > > ___ > 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. -- Chris Albertson Redondo Beach, California ___ 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] Adafruit Ultimate GPS timing message arrival times
Well, the whole point of the exercise is to see how well you can do if you DON'T have an internet connection, a 1PPS signal, or a stratum 1 time server available... only the humble messages coming from a 10 dollar GPS receiver. Try getting a net connection in the middle of the Gobi desert (where one user uses Lady Heather's time sync feature to keep their system clocks reasonably accurate). If you can put the receiver into a binary message mode, you can usually do better than NMEA (but, surprisingly, usually not by much). And by selecting a receiver that has known good / stable message timing you can do surprisingly well. -- > I feel that using the serial NMEA stream would, today, be a last resort, as > an Internet sync would be considerably better. Would you agree with that? ___ 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] Effect of EFC noise on phase noise
On Mon, 1 Aug 2016 11:21:10 -0400 KA2WEU--- via time-nuts wrote: > A good filter in the cable is highly recommended, 5 KOhm & 1000 uF cleans > many things Uhmm.. with 1mF in capacitors... don't you run into into microphonics problems? Or all these capacitors supposed to be tantalum/aluminium caps? Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ 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] Effect of EFC noise on phase noise
Hi ….. until you discover that you picked the *wrong* capacitor manufacturer and you have more noise from leakage in the cap than you did to start out with :) In general “big C and small R” is the better solution than “big R and small C”. The pesky part is that with electrolytic caps, the whole “noise current” thing changes as the voltage moves around. You go to measure things and by the time the gear is set up, the noise has dropped. Turn it all off, come back the next day and it’s noisy again. An even more subtle issue can be capacitor temperature coefficient on really long Tau filters. If C changes (due to temperature fluxuations) faster than the settling time of the filter, you get noise. Charge is the same so delta C gives delta V. I *wish* I could tell you that was all purely theoretical. Unfortunately it’s based on empirical data collected in the “how could I be so stupid” fashion. Bob > On Aug 1, 2016, at 11:21 AM, KA2WEU--- via time-nuts > wrote: > > A good filter in the cable is highly recommended, 5 KOhm & 1000 uF cleans > many things > > > In a message dated 8/1/2016 11:12:51 A.M. Eastern Daylight Time, > kb...@n1k.org writes: > > Hi > > It’s just very standard FM modulation math. The only gotcha is the > (often unknown) bandwidth of the EFC port. Even on a precision > OCXO, it might be <10 Hz, it might be over a KHz …. The trap many > fall into is the “small angle” restriction. You can get into modulation > indexes that will get the second and third order terms contributing. > It’s more common to see on vibration, but it can happen on a noisy > EFC. > > Bob > > >> On Aug 1, 2016, at 9:46 AM, Attila Kinali wrote: >> >> Moin, >> >> I need some formulas that relate EFC noise to the (added) phase noise of >> an OCXO. It shouldn't be too difficult to come up with something. But >> before I make some stupid mistakes, i wanted to ask whether someone >> has already done this or has any references to papers? My google-foo >> was not strong enough to find something. >> >> Attila Kinali >> >> -- >> It is upon moral qualities that a society is ultimately founded. All >> the prosperity and technological sophistication in the world is of no >> use without that foundation. >>-- Miss Matheson, The Diamond Age, Neil Stephenson >> ___ >> 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 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] Effect of EFC noise on phase noise
A good filter in the cable is highly recommended, 5 KOhm & 1000 uF cleans many things In a message dated 8/1/2016 11:12:51 A.M. Eastern Daylight Time, kb...@n1k.org writes: Hi It’s just very standard FM modulation math. The only gotcha is the (often unknown) bandwidth of the EFC port. Even on a precision OCXO, it might be <10 Hz, it might be over a KHz …. The trap many fall into is the “small angle” restriction. You can get into modulation indexes that will get the second and third order terms contributing. It’s more common to see on vibration, but it can happen on a noisy EFC. Bob > On Aug 1, 2016, at 9:46 AM, Attila Kinali wrote: > > Moin, > > I need some formulas that relate EFC noise to the (added) phase noise of > an OCXO. It shouldn't be too difficult to come up with something. But > before I make some stupid mistakes, i wanted to ask whether someone > has already done this or has any references to papers? My google-foo > was not strong enough to find something. > > Attila Kinali > > -- > It is upon moral qualities that a society is ultimately founded. All > the prosperity and technological sophistication in the world is of no > use without that foundation. > -- Miss Matheson, The Diamond Age, Neil Stephenson > ___ > 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 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] Q/noise of Earth as an oscillator
Hi Jim.
> You said: "you need energy; you need energy loss; you need cycles over which
> that loss repeatedly occurs."
> With regard to the earth, where is the first one?
By first one, do you mean where does the initial energy come from?
For a pendulum clock, you supply energy with a lift or a push. For a lift to
the side, E = mgh, where h is the height above the base. For a push from
center, E = 1/2 mv^2. Either way, it takes all the potential or kinetic E you
provide and starts making time from there.
For a rotating clock, you just give it a twist. In this case, E = 1/2 Iw^2,
where I is the moment of inertia and w (omega) is angular velocity. For earth
the total E is 2.1e29 J. That's the energy number you want, yes?
> Sure it was there at the start when the solar system formed, but where is it
> now?
I don't have data on where the initial swirl of solar system mass came from, or
how much of that rotational energy went into our planet and its pesky moon, or
Who or what gave that initial twist. The Q is pretty high so I assume you could
work backwards, but I leave that to astronomers and cosmologists. I believe the
2 ms/day / century estimate we use is one such measurement.
For more on earth rotation rate, UTC and leap seconds see
https://www.ucolick.org/~sla/leapsecs/dutc.html
Surely in the literature there is a pile of information or speculation
regarding all the rotational energy in the universe. It seems a common theme
everywhere you look; maybe it was as much Big Twist as Big Bang? Perhaps in
your Pulsar research you've run across some papers you could share. Off-list is
ok, unless you think it has general time-nuts appeal. We're running the risk of
spinning off-topic already.
Thanks,
/tvb
- Original Message -
From: "Jim Palfreyman"
To: "Discussion of precise time and frequency measurement"
Sent: Sunday, July 31, 2016 7:34 PM
Subject: Re: [time-nuts] Q/noise of Earth as an oscillator
Hi Tom,
You said: "you need energy; you need energy loss; you need cycles over
which that loss repeatedly occurs."
With regard to the earth, where is the first one? Sure it was there at the
start when the solar system formed, but where is it now?
Jim
On 1 August 2016 at 12:16, Tom Van Baak wrote:
> Hal:
> > Is there a term other than Q that is used to describe the rate of energy
> loss
> > for things that aren't oscillators?
>
> Jim:
> > cooling (as in hot things)
> > discharge (as in capacitors and batteries)
> > leakage (as in pressure vessels)
> > loss
>
> Scott:
> > An irreversible process would be a better description versus energy loss.
> > Like joule heating (resistance, friction).
>
> Notice that these are all energy losses over time; gradual processes with
> perhaps an exponential time constant, but without cycles or periods. We
> know not to apply Q in these scenarios.
>
> But when you have an oscillator, or a resonator, or (as I suggest) a
> "rotator", it seems to make sense to use Q to describe the normalized rate
> of decay. So three keys to Q: you need energy; you need energy loss; you
> need cycles over which that loss repeatedly occurs.
>
> We use units of time (for example, SI seconds) when we describe a rate.
> But here's why Q is unitless -- you normalize the energy (using E / dE)
> *and* you also normalize the time (by cycle). No Joules. No seconds. So
> having period is fundamental to Q. It's this unitless character of Q (in
> both energy and time) that makes it portable from one branch of science to
> another. And if you measure in radians you can even get rid of the 2*pi
> factor ;-)
>
> Without controversy, lots of articles define Q as 2*pi times {total
> energy} / {energy lost per cycle}. To me, a slowly decaying spinning Earth
> meets the three criteria. It appears to follow both the letter and the
> spirit of Q.
>
> Bob:
> > ummm…. Q is the general term of rate of energy loss and we just happen
> to apply
> > it to oscillators in a very elegant fashion….
>
> Oh, no. Now we have both quality factor and elegance factor!
>
> /tvb
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- Original Message -
From: "Jim Palfreyman"
To: "Discussion of precise time and frequency measurement"
Sent: Sunday, July 31, 2016 7:34 PM
Subject: Re: [time-nuts] Q/noise of Earth as an oscillator
Hi Tom,
You said: "you need energy; you need energy loss; you need cycles over
which that loss repeatedly occurs."
With regard to the earth, where is the first one? Sure it was there at the
start when the solar system formed, but where is it now?
Jim
On 1 August 2016 at 12:16, Tom Van Baak wrote:
Re: [time-nuts] Effect of EFC noise on phase noise
On Mon, 01 Aug 2016 14:36:28 + "Poul-Henning Kamp" wrote: > >I need some formulas that relate EFC noise to the (added) phase noise of > >an OCXO. It shouldn't be too difficult to come up with something. But > >before I make some stupid mistakes, i wanted to ask whether someone > >has already done this or has any references to papers? My google-foo > >was not strong enough to find something. > > Isn't that just FM modulation ? Yes, it is. The problem is not the theory. The problem is to calculate the correct values. I know i can figure it out, but if there are ready to use formulas that are known to be correct, I rather use those. Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ 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] Adafruit Ultimate GPS timing message arrival times
On Mon, Aug 1, 2016 at 3:01 AM, Hal Murray wrote: > Depends on your internet connection and/or the specific GPS module you are > using. > > I don't know of any good GPS modules that use NMEA. I do know of really > crappy internet connections. Bufferbloat is the buzzword. > Bufferbloat is an issue but the NTP problem is unknown assymetric delays. If you're a bit flexible regarding "module" you can do quite well using NMEA. Both points are shown in the output below (sent using a constant width font). FURY is a Fury, offset and jitter in milliseconds. $ ntpq -p remote refid st t when poll reach delay offset jitter == oPPS(0) .GPPS. 0 l38 3770.000 -0.002 0.003 *GPS_NMEA(0) .FURY. 0 l28 3770.000 -0.010 0.018 time-d.nist.gov .ACTS. 1 u 264 512 353 105.770 29.742 0.348 +nub .GPPS. 1 s4 16 3770.151 -0.025 0.022 Compared to the MTK3xxx in the Adafruit UGPS circa 2-3 years ago. remote refid st t when poll reach delay offset jitter == oPPS(0) .GPPS. 0 l48 3770.0000.002 0.004 *GPS_NMEA(0) .ADAU. 0 l38 3770.000 -78.472 25.623 ___ 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] Effect of EFC noise on phase noise
Hi It’s just very standard FM modulation math. The only gotcha is the (often unknown) bandwidth of the EFC port. Even on a precision OCXO, it might be <10 Hz, it might be over a KHz …. The trap many fall into is the “small angle” restriction. You can get into modulation indexes that will get the second and third order terms contributing. It’s more common to see on vibration, but it can happen on a noisy EFC. Bob > On Aug 1, 2016, at 9:46 AM, Attila Kinali wrote: > > Moin, > > I need some formulas that relate EFC noise to the (added) phase noise of > an OCXO. It shouldn't be too difficult to come up with something. But > before I make some stupid mistakes, i wanted to ask whether someone > has already done this or has any references to papers? My google-foo > was not strong enough to find something. > > Attila Kinali > > -- > It is upon moral qualities that a society is ultimately founded. All > the prosperity and technological sophistication in the world is of no > use without that foundation. > -- Miss Matheson, The Diamond Age, Neil Stephenson > ___ > 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] Effect of EFC noise on phase noise
In message <20160801154643.905ed816ac900a8d9a505...@kinali.ch>, Attila Kinali w rites: >I need some formulas that relate EFC noise to the (added) phase noise of >an OCXO. It shouldn't be too difficult to come up with something. But >before I make some stupid mistakes, i wanted to ask whether someone >has already done this or has any references to papers? My google-foo >was not strong enough to find something. Isn't that just FM modulation ? -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ 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] Effect of EFC noise on phase noise
Moin, I need some formulas that relate EFC noise to the (added) phase noise of an OCXO. It shouldn't be too difficult to come up with something. But before I make some stupid mistakes, i wanted to ask whether someone has already done this or has any references to papers? My google-foo was not strong enough to find something. Attila Kinali -- It is upon moral qualities that a society is ultimately founded. All the prosperity and technological sophistication in the world is of no use without that foundation. -- Miss Matheson, The Diamond Age, Neil Stephenson ___ 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] Very Accurate Delta Time RF Pulse Measurements
Have you looked at the blitzortung.org system? There may be some ideas to glean from that On July 28, 2016 6:12:54 PM CDT, Jerome Blaha wrote: >Hi Guys, > >This is a little outside of time-nuts scope, but not by much. I'm >interested in finding the time between two rising edges above a set >threshold with preferably nS or high ps timing accuracy. Can this be >simply done with a few programmed Microchip PICs or with a good short >term OCXO clock? The issue I see is that a 10Mhz timing reference with >1 cycle difference in time yields 100ns resolution, which is far too >large, so maybe a PIC can solve this. > >This weekend project would be a multi-element antenna array, each with >a super-fast response log peak power detector fed into several PICs for >time of arrival. Whenever a nearby high energy RF pulse is detected, >the time of arrival between two antenna elements and hence the >direction toward the TX could be roughly computed. Some typical log >peak detectors have an 8ns input pulse response time, so I'm hoping >that rise times are similar between multiple detectors, negating the >delayed response. > >There are time of arrival/AoA systems out there with synthetic doppler, >phased arrays, correlative interferometers, and phase comparators, but >it would be interesting to accomplish super wideband AoA timing on two >rising pulses with relatively cheap parts. > >Thanks, > >-Jerome >___ >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. -- Sent from my Moto-X wireless tracker while I do other things. ___ 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] Adafruit Ultimate GPS timing message arrival times
david-tay...@blueyonder.co.uk said: > From your data and my own measurements, I feel that using the serial NMEA > stream would, today, be a last resort, as an Internet sync would be > considerably better. Would you agree with that? Depends on your internet connection and/or the specific GPS module you are using. I don't know of any good GPS modules that use NMEA. I do know of really crappy internet connections. Bufferbloat is the buzzword. -- These are my opinions. I hate spam. ___ 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.
