Re: [time-nuts] GPS to H-Maser comparison
Truly astonishing. I see nothing in my ntp gps data and unfortunately was not logging my thunderbolt. Le 4 oct. 2013 à 05:56, Jim Palfreyman a écrit : Hi all, If you go to this page: http://users.on.net/~cdadsl/ you will see some graphs (all in UT). Notice the larger than usual bump on Oct 02 around 0600 ish. The names are locations all over Australia. I never thought I'd have to do this. Yaragadee should have two r's Jim Palfreyman On Friday, 4 October 2013, Brian Inglis wrote: On 2013-10-03 05:33, Jim Palfreyman wrote: Noticed an above average bump in our H-Maser vs GPS graphs - from sites all over Australia. Recent coronal mass ejection or US government shutdown not updating GPS? Anyone else seen it? drop out gap between about 04.21-04.26 UTC? clockstats.20131003: 56568 15684.876 127.127.20.4 $GPRMC 042124 A ... 56568 16004.862 127.127.20.4 $GPRMC 042644 A ... peerstats.20131003: 56568 15684.876 127.127.20.4 961a -0.02270 ... 0.05344 56568 16004.862 127.127.20.4 961a -0.13150 ... 0.15721 loopstats.20131003: 56568 15684.876 -0.02270 0.899 0.07071 0.70 4 56568 16004.862 -0.13150 0.898 0.08830 0.000114 4 __**_ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/** mailman/listinfo/time-nutshttps://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] A man with two clocks...
No, my code is not posted anywhere but I would be glad to email it to anyone interested. Cheers, Graham -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Phil Genera Sent: October-03-13 6:44 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] A man with two clocks... Is your code posted anywhere? I've been meaning to do roughly the same. -- Phil On Oct 3, 2013 12:07 PM, Collins, Graham coll...@navcanada.ca wrote: David, Your raspberry-pi NTP clock is very cool. I have put together something along the same line but is in reality just a network connected NTP disciplined clock display using an Arduino and a typical 16x2 LCD housed in a small project box. The Arduino has a network shield and get's it power from a USB port although it could be powered by a battery or wall wart type of supply. When it starts, the device attempts to get an IP address using DHCP. Once that is sorted it attempts to sync to my local GPS disciplined NTP server, then sets and displays it's time. It resyncs every some value between 15 and 30 minutes with the NTP server. If ever my local NTP server can't be found, it will attempt to sync to an outside NTP server on the internet. It keeps pretty good time, not time nuts level but is always within a few tenths of a second which is suitable for it's intended purpose. Basic time keeping of the Arduino uses it's 16MHz crystal clock and there is some provision for adjusting in code which I have done to improve it's time keeping. I am toying with the idea of adding a 1 PPS input but just haven't gotten round to it yet. All the bits and pieces of the code was copied from existing projects and libraries it being just a matter of finding the appropriate bits and pieces, putting them together and making changes in a few places to improve it's time keeping. It was a fun project to put together and has proven so useful in my lab that I will probably put together a couple more. Cheers, Graham ve3gtc === Max, I see similar things here. I've always put it down to relatively poor circuitry in the radio clock, which is why I built my NTP-controlled wall clock! http://www.satsignal.eu/raspberry-pi/DigitalClock.html One radio clock is below. That particular MSF clock is actually not too bad - visibly it's in sync with the NTP clock (which itself is within a few microseconds of GPS time). 73, David GM8ARV -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk . ___ 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] A man with two clocks...
Max, This is a very interesting project and well documented, thank you! Didier KO4BB David J Taylor david-tay...@blueyonder.co.uk wrote: Among my time nut toys is a Consumer grade GPS clock and a similar WWVB clock. The WWVB clock consistently runs about 0.2 seconds ahead of the GPS one. I know no one can say why without knowing the particulars of the two clock's circuits. Just thought I'd post it for what it's worth. Regards. Max. K 4 O DS. === Max, I see similar things here. I've always put it down to relatively poor circuitry in the radio clock, which is why I built my NTP-controlled wall clock! http://www.satsignal.eu/raspberry-pi/DigitalClock.html One radio clock is below. That particular MSF clock is actually not too bad - visibly it's in sync with the NTP clock (which itself is within a few microseconds of GPS time). 73, David GM8ARV -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ 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 Motorola Droid Razr 4G LTE 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] GPSDO choices
The Novus at www.synreference.net Sent from my iPhone On Oct 3, 2013, at 11:24 PM, Paul tic-...@bodosom.net wrote: I'm looking for a new, ready to go, inexpensive desktop GPSDO. So far I've only found the Fury and Thunderbolt E. Are there other reasonable choices e.g. the J R Miller (although I'm not sure there's a source of new TU-30 parts). Thanks. -- Paul *Say $2k ___ 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] FTS 4060 Cesium Time Frequency Standard, Datum
On 10/2/2013 10:34 PM, time-nuts-requ...@febo.com wrote: Hi guys, I am going to pull it apart this weekend and do some more exploring. Hope to get some pictures for reference. I think I will make up some extender cables so I can operate the CBT assembly away from the main chassis. That should make things a bit easier to look at. Thanks, Tom Just to clarify, CBT, is Cesium Beam Tube right? I made the mistake of searching for that acronym, and ended up with some very different results. Not time related results... Dan ___ 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] GPSDO choices
Hi Paul, I purchased one of the Miller units and it more than met my expectations (that were set by the description on his web site and the information I was able to find on the web.) I also purchased a Fury which also more than met my expectations. I would have no issues repeating either purchase. Depending on your needs and budget both units could be reasonable choices. For what it is worth when I purchased the Miller unit I was looking for a 10 Mhz frequency standard for use with my amateur radios, when I purchased the Fury I was looking for a new GPSDO for time nuts hobby useage. I also own several other GPSDO's including a surplus Thunderbolt. The nominal 12 Volt power requirements of both the Miller and Fury units are a plus for me but in practice I have never run my Fury from any source other than the power supply that was shipped with it. If you would like more specfic info feel free to contact me off list and I can try to help. Regards Mark Spencer -- On Oct 3, 2013, at 11:24 PM, Paul tic-...@bodosom.net wrote: Iapos;m looking for a new, ready to go, inexpensive desktop GPSDO. So far Iapos;ve only found the Fury and Thunderbolt E. Are there other reasonable choices e.g. the J R Miller (although Iapos;m not sure thereapos;s a source of new TU-30 parts). Thanks. -- Paul *Say $2k ___ 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] FTS 4060 Cesium Time Frequency Standard, Datum
Hi Dan, Yes, it is Cesium Beam Tube. Maybe someone can tell me the best way to search the time-nuts archive. Do you need to download all the files to a common DB? Regards, Tom - Original Message - From: Dan Kemppainen d...@irtelemetrics.com To: time-nuts@febo.com Sent: Friday, October 04, 2013 8:23 AM Subject: Re: [time-nuts] FTS 4060 Cesium Time Frequency Standard, Datum On 10/2/2013 10:34 PM, time-nuts-requ...@febo.com wrote: Hi guys, I am going to pull it apart this weekend and do some more exploring. Hope to get some pictures for reference. I think I will make up some extender cables so I can operate the CBT assembly away from the main chassis. That should make things a bit easier to look at. Thanks, Tom Just to clarify, CBT, is Cesium Beam Tube right? I made the mistake of searching for that acronym, and ended up with some very different results. Not time related results... Dan ___ 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] trimble antenna connector
why do older thunderbolts use an F connector for the antenna? (the current version uses a BNC). It seems like it needlessly complicates installation at a base station. I've always wondered this. -- --Eric _ Eric Garner ___ 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] exponential+linear fit
I'm trying to find a good way to do a combination exponential/linear fit (for baseline removal). It's modeling phase for a moving source plus a thermal transient, so the underlying physics is the linear term (the phase varies linearly with time, since the velocity is constant) plus the temperature effect. the general equation is y(t) = k1 + k2*t + k3*exp(k4*t) Working in matlab/octave, but that's just the tool, I'm looking for some numerical analysis insight. I could do it in steps.. do a straight line to get k1 and k2, then fit k3 k4 to the residual; or fit the exponential first, then do the straight line., but I'm not sure that will minimize the error, or if it matches the underlying model (a combination of a linear trend and thermal effects) as well. I suppose I could do something like do the fit on the derivative, which would be y'(t) = k2 + k3*k4*exp(k4*t) Then solve for the the k1. In reality, I don't think I care as much what the numbers are (particularly the k1 DC offset) so could probably just integrate (numerically) y'()-k2-k3*k4*exp(k4*t) and get my sequence with the DC term, linear drift, and exponential component removed. The fear I have is that differentiating emphasizes noise. ___ 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] trimble antenna connector
Hi Trimble recommend 75R CATV or similar cable for the Thunderbolt as it's lower loss (even with the mismatch loss to 50R it's an advantage), hence the F type plugs. Adaptors are cheap and available even here in the UK where the F type is a fairly new entry into the market. Using 75R cable with F plugs is even easier. Robert G8RPI. From: Eric Garner garn...@gmail.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, 4 October 2013, 17:38 Subject: [time-nuts] trimble antenna connector why do older thunderbolts use an F connector for the antenna? (the current version uses a BNC). It seems like it needlessly complicates installation at a base station. I've always wondered this. -- --Eric _ Eric Garner ___ 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] trimble antenna connector
Hi Eric, Because they were designed to use cheap 75ohm cable-tv/satellite cables which usually go with F connectors. The companion Bullet antenna also have F connector. From the Tbolt manual RG-59 is a 75 ohm coaxial cable. The ThunderBolt and Bullet II HE antenna are compatible with 75 ohm cable. Compared to most 50 ohm cable, 75 ohm cable provides superior transmissibility for the 1.5 GHz GPS signal and a better quality cable for the price. Mismatched impedance is not a problem. -- Björn why do older thunderbolts use an F connector for the antenna? (the current version uses a BNC). It seems like it needlessly complicates installation at a base station. I've always wondered this. -- --Eric _ Eric Garner ___ 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] trimble antenna connector
They recommended using 75 ohm TV cable with F connectors as being low-loss and cheap. The 50-75 ohm mismatch is negligible in this application. David On 10/4/13 12:38 PM, Eric Garner wrote: why do older thunderbolts use an F connector for the antenna? (the current version uses a BNC). It seems like it needlessly complicates installation at a base station. I've always wondered this. ___ 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] exponential+linear fit
Hello, Jim, On Fri, 4 Oct 2013, Jim Lux wrote: I'm trying to find a good way to do a combination exponential/linear fit (for baseline removal). It's modeling phase for a moving source plus a thermal transient, so the underlying physics is the linear term (the phase varies linearly with time, since the velocity is constant) plus the temperature effect. the general equation is y(t) = k1 + k2*t + k3*exp(k4*t) Working in matlab/octave, but that's just the tool, I'm looking for some numerical analysis insight. (...etc) The control estimation practice is to model such a disturbance as a response of LTI system to, in your particular case, (almost) deterministic excitation. Specifically, the exp() term is a response of 1st-order lowpass (1/(1+s*T). The k1+k2*t is a response of double cascaded integrator (1/s^2). If you need to fit the model to data, the inputs to the subsystems should be found (inverse filtration for simple systems, spectral factorization and inverse filtration for the more complicated ones). If you don't know the T, a greybox identification should be done in addition. What is interesting: the model and often also the fit methods are the same either for the deterministic signal (such as your y(t)), as well as for the stochastic signals, like colored noise. Following statements from optimal estimation theory, both white noise as well as Dirac (delta) function share some common properties w.r.t. to LTI system description, and it is enoiugh to describe (and fit, estimate, etc.) then with the same tools. (Of course, this is limited to the linear system domain, L2 criterions etc.) Similar matter of clock drifts have been briefly discussed in our recent paper, dealing with two-clock ensembling: Clock Composition by Wiener Filtering Illustrated on Two Atomic Clocks (M.Peca, V.Michalek, M.Vacek) http://rtime.felk.cvut.cz/~pecam1/eftf/ In case of interest, feel free to contact me directly. Best regards, Marek ___ 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] trimble antenna connector
I expect because the cable that was used was RG-6 and the easiest (read: cheapest) connector was the F connector. How would you like to see your cable installer work with BNC connectors !! 73, Dick, W1KSZ On 10/4/2013 9:38 AM, Eric Garner wrote: why do older thunderbolts use an F connector for the antenna? (the current version uses a BNC). It seems like it needlessly complicates installation at a base station. I've always wondered this. ___ 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 1 GHz low phase noise amplifier
Thanks for the info. I wouldn't have suspected those little gain blocks were so good, and the voltage bias problem makes sense. Rick On 9/30/2013 5:53 AM, Garry Thorp wrote: Mini-Circuits' GALI- series of InGaP MMICs work pretty well. They typically have ~4dB NF, and the noise performance seems to be maintained up to a couple of dB below 1dB compression. I haven't measured added phase noise, but absolute phase noise measurements, where the MMICs are used to amplify multiplied-up crystal oscillators, appear to indicate added noise less than -180dBc/Hz at 10kHz offset when scaled to 120MHz (using 20log(N) relationship). The GALI- series are traditional MMICs that require a resistor or current source to bias them. We have had problems with Some TriQuint InGaP MMICs that are designed for voltage biasing. Noise from their internal bias circuitry seems to get on to the signal, and the NF started to increase well below compression. Mini-Circuits' GVA- series may well be similar, as they are also voltage-biased. Garry Thorp Date: Fri, 27 Sep 2013 10:53:10 -0700 From: Richard Karlquist rich...@karlquist.commailto:rich...@karlquist.com Can anyone suggest a low phase noise amplifier covering something like 10-1000 MHz? Gain should be 10 to 20 dB and phase noise should be spec'ed at +10 to +13 dBm output. Both close in and far out phase noise are of interest. Thanks in advance. Rick Karlquist ___ 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] FTS 4060 Cesium Time Frequency Standard, Datum
On 10/4/2013 9:41 AM, Tom Miller wrote: Maybe someone can tell me the best way to search the time-nuts archive. Do you need to download all the files to a common DB? Regards, Tom I usually use this for time-nuts searches... http://www.mail-archive.com/time-nuts@febo.com/info.html ___ 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] exponential+linear fit
On Fri, 04 Oct 2013 14:30:40 -0400, time-nuts-requ...@febo.com wrote: -- Message: 4 Date: Fri, 04 Oct 2013 10:38:07 -0700 From: Jim Lux jim...@earthlink.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] exponential+linear fit Message-ID: 524efcff.8000...@earthlink.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed I'm trying to find a good way to do a combination exponential/linear fit (for baseline removal). It's modeling phase for a moving source plus a thermal transient, so the underlying physics is the linear term (the phase varies linearly with time, since the velocity is constant) plus the temperature effect. the general equation is y(t) = k1 + k2*t + k3*exp(k4*t) Working in matlab/octave, but that's just the tool, I'm looking for some numerical analysis insight. I could do it in steps.. do a straight line to get k1 and k2, then fit k3 k4 to the residual; or fit the exponential first, then do the straight line., but I'm not sure that will minimize the error, or if it matches the underlying model (a combination of a linear trend and thermal effects) as well. I suppose I could do something like do the fit on the derivative, which would be y'(t) = k2 + k3*k4*exp(k4*t) Then solve for the the k1. In reality, I don't think I care as much what the numbers are (particularly the k1 DC offset) so could probably just integrate (numerically) y'()-k2-k3*k4*exp(k4*t) and get my sequence with the DC term, linear drift, and exponential component removed. The fear I have is that differentiating emphasizes noise. How many measured data points do you have? If you have enough data, you can use the MatLab nlinfit() (nonlinear fit) function to fit the data directly to the y(t) equation. Because nlinfit uses a least-squares approach, and there are many coefficients to be found, a reasonable starting point is required. The fit on the derivative, while probably too noisy to yield a useful final answer, would be one way to get some of the initial values. I did just this recently, fitting a skew gaussian pdf to a histogram, using rough mean, standard deviation, and skewness computed from the histogram to seed nlinfit. The mean, standard deviation, and skewness computed from the histogram are famously inaccurate if there is significant skew, but it was still good enough to keep nlinfit from getting lost. Joe Gwinn ___ 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] GPSDO choices
Paul, I picked up a TrueTime XL-AK for under $200 on eBay a couple of years ago. Advertised at better than 1 x 10 -12. RS232 interface and 1 PPS out as well as 10 mhz out and many options. Seems to work well with any of the 5 volt antennas I've used. One rack unit high. Have been quite happy with it but then, maybe I don't know any better. Al Wolfe I'm looking for a new, ready to go, inexpensive desktop GPSDO. So far I've only found the Fury and Thunderbolt E. Are there other reasonable choices e.g. the J R Miller (although I'm not sure there's a source of new TU-30 parts). Thanks. -- Paul *Say $2k ___ 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] trimble antenna connector
You might TDR an F connector splice once. the F connectors are really pretty good. Tom - Original Message - From: Richard Solomon w1...@earthlink.net To: time-nuts@febo.com Sent: Friday, October 04, 2013 3:26 PM Subject: Re: [time-nuts] trimble antenna connector I expect because the cable that was used was RG-6 and the easiest (read: cheapest) connector was the F connector. How would you like to see your cable installer work with BNC connectors !! 73, Dick, W1KSZ On 10/4/2013 9:38 AM, Eric Garner wrote: why do older thunderbolts use an F connector for the antenna? (the current version uses a BNC). It seems like it needlessly complicates installation at a base station. I've always wondered this. ___ 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] exponential+linear fit
On 10/4/13 1:18 PM, Joseph Gwinn wrote: On Fri, 04 Oct 2013 14:30:40 -0400, time-nuts-requ...@febo.com wrote: -- Message: 4 Date: Fri, 04 Oct 2013 10:38:07 -0700 From: Jim Lux jim...@earthlink.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] exponential+linear fit Message-ID: 524efcff.8000...@earthlink.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed I'm trying to find a good way to do a combination exponential/linear fit (for baseline removal). It's modeling phase for a moving source plus a thermal transient, so the underlying physics is the linear term (the phase varies linearly with time, since the velocity is constant) plus the temperature effect. the general equation is y(t) = k1 + k2*t + k3*exp(k4*t) Working in matlab/octave, but that's just the tool, I'm looking for some numerical analysis insight. I could do it in steps.. do a straight line to get k1 and k2, then fit k3 k4 to the residual; or fit the exponential first, then do the straight line., but I'm not sure that will minimize the error, or if it matches the underlying model (a combination of a linear trend and thermal effects) as well. I suppose I could do something like do the fit on the derivative, which would be y'(t) = k2 + k3*k4*exp(k4*t) Then solve for the the k1. In reality, I don't think I care as much what the numbers are (particularly the k1 DC offset) so could probably just integrate (numerically) y'()-k2-k3*k4*exp(k4*t) and get my sequence with the DC term, linear drift, and exponential component removed. The fear I have is that differentiating emphasizes noise. How many measured data points do you have? If you have enough data, you can use the MatLab nlinfit() (nonlinear fit) function to fit the data directly to the y(t) equation. I'm removing a slowly varying bias term from fairly noisy data. Maybe several 10s of thousands of data points, And I want to do it quickly on a slow processor. Because nlinfit uses a least-squares approach, and there are many coefficients to be found, a reasonable starting point is required. The fit on the derivative, while probably too noisy to yield a useful final answer, would be one way to get some of the initial values. I've done that and it works.. but I'm looking for a more basic sort of approach, given that I actually know something about the underlying model. I did just this recently, fitting a skew gaussian pdf to a histogram, using rough mean, standard deviation, and skewness computed from the histogram to seed nlinfit. The mean, standard deviation, and skewness computed from the histogram are famously inaccurate if there is significant skew, but it was still good enough to keep nlinfit from getting lost. ___ 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] exponential+linear fit
Hi Joe that sounds like a system I was thinking of suggesting to Jim. I wrote some iterative code on a time share bureau machine in the late60s. make a guess at kx values and let the prog spit out k values for a dk/dt minimum then chose another set of starters an see if it finishes in the same place. A given local minimum may not be the lowest. Its crude but very effective. My boss didnt believe it and employed a mathematician who did not understand the physics to get it wrong ! this was fitting to similar type equation an Arhennius equation (if I remembered how to spell him :-)) A friendly mathematician called it the BFI technique Alan G3NYK - Original Message - From: Joseph Gwinn joegw...@comcast.net To: time-nuts@febo.com Sent: Friday, October 04, 2013 9:18 PM Subject: Re: [time-nuts] exponential+linear fit On Fri, 04 Oct 2013 14:30:40 -0400, time-nuts-requ...@febo.com wrote: -- Message: 4 Date: Fri, 04 Oct 2013 10:38:07 -0700 From: Jim Lux jim...@earthlink.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] exponential+linear fit Message-ID: 524efcff.8000...@earthlink.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed I'm trying to find a good way to do a combination exponential/linear fit (for baseline removal). It's modeling phase for a moving source plus a thermal transient, so the underlying physics is the linear term (the phase varies linearly with time, since the velocity is constant) plus the temperature effect. the general equation is y(t) = k1 + k2*t + k3*exp(k4*t) Working in matlab/octave, but that's just the tool, I'm looking for some numerical analysis insight. I could do it in steps.. do a straight line to get k1 and k2, then fit k3 k4 to the residual; or fit the exponential first, then do the straight line., but I'm not sure that will minimize the error, or if it matches the underlying model (a combination of a linear trend and thermal effects) as well. I suppose I could do something like do the fit on the derivative, which would be y'(t) = k2 + k3*k4*exp(k4*t) Then solve for the the k1. In reality, I don't think I care as much what the numbers are (particularly the k1 DC offset) so could probably just integrate (numerically) y'()-k2-k3*k4*exp(k4*t) and get my sequence with the DC term, linear drift, and exponential component removed. The fear I have is that differentiating emphasizes noise. How many measured data points do you have? If you have enough data, you can use the MatLab nlinfit() (nonlinear fit) function to fit the data directly to the y(t) equation. Because nlinfit uses a least-squares approach, and there are many coefficients to be found, a reasonable starting point is required. The fit on the derivative, while probably too noisy to yield a useful final answer, would be one way to get some of the initial values. I did just this recently, fitting a skew gaussian pdf to a histogram, using rough mean, standard deviation, and skewness computed from the histogram to seed nlinfit. The mean, standard deviation, and skewness computed from the histogram are famously inaccurate if there is significant skew, but it was still good enough to keep nlinfit from getting lost. Joe Gwinn ___ 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] exponential+linear fit
Jim it may not be helpful but had you thoughtof expanding the exponential as the first few terms of an infinite series to see if it simplifies fitting? Alan G3NYK - Original Message - From: Jim Lux jim...@earthlink.net To: time-nuts@febo.com Sent: Friday, October 04, 2013 10:16 PM Subject: Re: [time-nuts] exponential+linear fit On 10/4/13 1:18 PM, Joseph Gwinn wrote: On Fri, 04 Oct 2013 14:30:40 -0400, time-nuts-requ...@febo.com wrote: -- Message: 4 Date: Fri, 04 Oct 2013 10:38:07 -0700 From: Jim Lux jim...@earthlink.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: [time-nuts] exponential+linear fit Message-ID: 524efcff.8000...@earthlink.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed I'm trying to find a good way to do a combination exponential/linear fit (for baseline removal). It's modeling phase for a moving source plus a thermal transient, so the underlying physics is the linear term (the phase varies linearly with time, since the velocity is constant) plus the temperature effect. the general equation is y(t) = k1 + k2*t + k3*exp(k4*t) Working in matlab/octave, but that's just the tool, I'm looking for some numerical analysis insight. I could do it in steps.. do a straight line to get k1 and k2, then fit k3 k4 to the residual; or fit the exponential first, then do the straight line., but I'm not sure that will minimize the error, or if it matches the underlying model (a combination of a linear trend and thermal effects) as well. I suppose I could do something like do the fit on the derivative, which would be y'(t) = k2 + k3*k4*exp(k4*t) Then solve for the the k1. In reality, I don't think I care as much what the numbers are (particularly the k1 DC offset) so could probably just integrate (numerically) y'()-k2-k3*k4*exp(k4*t) and get my sequence with the DC term, linear drift, and exponential component removed. The fear I have is that differentiating emphasizes noise. How many measured data points do you have? If you have enough data, you can use the MatLab nlinfit() (nonlinear fit) function to fit the data directly to the y(t) equation. I'm removing a slowly varying bias term from fairly noisy data. Maybe several 10s of thousands of data points, And I want to do it quickly on a slow processor. Because nlinfit uses a least-squares approach, and there are many coefficients to be found, a reasonable starting point is required. The fit on the derivative, while probably too noisy to yield a useful final answer, would be one way to get some of the initial values. I've done that and it works.. but I'm looking for a more basic sort of approach, given that I actually know something about the underlying model. I did just this recently, fitting a skew gaussian pdf to a histogram, using rough mean, standard deviation, and skewness computed from the histogram to seed nlinfit. The mean, standard deviation, and skewness computed from the histogram are famously inaccurate if there is significant skew, but it was still good enough to keep nlinfit from getting lost. ___ 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] exponential+linear fit
Dear Jim, I'm removing a slowly varying bias term from fairly noisy data. Maybe several 10s of thousands of data points, And I want to do it quickly on a slow processor. I think the LTI framework should work very well for that; easy fixpoint implementation etc. Since I am a space fan, I'd be happy to try my tools. Would you like to send me the data? I've done that and it works.. but I'm looking for a more basic sort of approach, given that I actually know something about the underlying model. One example of such an estimator (working real-time), which I did in 2008: http://www.youtube.com/watch?v=Di4yG6ZRV3k Only the exp() term is missing here, the rest is same -- and besides the position and heading, it contains also 2nd order clock estimation -- similar way as in the GNSS. Best regards, Marek ___ 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] exponential+linear fit (Joseph Gauthier)
You might like this free MATLAB toolbox: http://www.mathworks.com.au/matlabcentral/fileexchange/24443-slm-shape-language-modeling Once you figure out how to use it, it works very well for all types of fits. ___ 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] A man with two clocks...
Still laughing. Actually I did it aurally. The GPS clock announces the time on the hour with a series of beeps similar to the old BBC time and the WWVB clock has an alarm which I can set to sound on the hour. The time interval is an estimation. Someday I will use a microphone connected to a storage oscilloscope to figure out what the difference is. Regards. Max. K 4 O DS. Email: m...@maxsmusicplace.com Transistor site http://www.funwithtransistors.net Vacuum tube site: http://www.funwithtubes.net Woodworking site http://www.angelfire.com/electronic/funwithtubes/Woodworking/wwindex.html Music site: http://www.maxsmusicplace.com To subscribe to the fun with transistors group send an email to. funwithtransistors-subscr...@yahoogroups.com To subscribe to the fun with tubes group send an email to, funwithtubes-subscr...@yahoogroups.com To subscribe to the fun with wood group send a blank email to funwithwood-subscr...@yahoogroups.com - Original Message - From: Tom Knox act...@hotmail.com To: Time-Nuts time-nuts@febo.com Sent: Thursday, October 03, 2013 1:46 PM Subject: Re: [time-nuts] A man with two clocks... It is all a matter of proper placement, now I know you are expecting a tirade on propagation delay and antenna placement and cable length. But actually my thought is to place them far enough apart with the WWV clock in front of your and your GPS at a 12-15 degree angle so it takes 0.2 second to look from one to the other. Thomas Knox From: david-tay...@blueyonder.co.uk To: time-nuts@febo.com Date: Thu, 3 Oct 2013 19:22:04 +0100 Subject: Re: [time-nuts] A man with two clocks... Among my time nut toys is a Consumer grade GPS clock and a similar WWVB clock. The WWVB clock consistently runs about 0.2 seconds ahead of the GPS one. I know no one can say why without knowing the particulars of the two clock's circuits. Just thought I'd post it for what it's worth. Regards. Max. K 4 O DS. === Max, I see similar things here. I've always put it down to relatively poor circuitry in the radio clock, which is why I built my NTP-controlled wall clock! http://www.satsignal.eu/raspberry-pi/DigitalClock.html One radio clock is below. That particular MSF clock is actually not too bad - visibly it's in sync with the NTP clock (which itself is within a few microseconds of GPS time). 73, David GM8ARV -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ 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.
