Re: [time-nuts] Setting Osc Frequencies
And Hal- what about the pcb layout for Bruce's 74CX version? Had time to look at it yet? It fell through the cracks when I got interested in something else. Is anybody really interested in that board? If so, please send me a reminder about the schematic. There have been lots of ideas kicked around recently. Is that still the right/best thing to build? I've used PCB Express, http://www.pcbexpress.com/ $125 for 10 boards, 2 layers, no solder mask, up to 9 sq inches $265 for solder mask and top silk screen. add $45 for silk on the bottom side Round up for shipping and taxes and whatever. -- These are my opinions, not necessarily my employer's. I hate spam. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Setting Osc Frequencies
Hal Murray wrote: And Hal- what about the pcb layout for Bruce's 74CX version? Had time to look at it yet? It fell through the cracks when I got interested in something else. Is anybody really interested in that board? If so, please send me a reminder about the schematic. There have been lots of ideas kicked around recently. Is that still the right/best thing to build? I've used PCB Express, http://www.pcbexpress.com/ $125 for 10 boards, 2 layers, no solder mask, up to 9 sq inches $265 for solder mask and top silk screen. add $45 for silk on the bottom side Round up for shipping and taxes and whatever. Hal For a simple no frills linear phase detector using an AD9901 (available from Digikey in the 44pin PLCC package)in the ECL mode is a better bet. It only requires a couple of slow linear amplifiers to scale the output. No comparators are necessary for the inputs. Just a few diodes capacitors and resistors are required to terminate the input cables and protect the differential clock inputs. If you want more bells and whistles such as programmable input dividers etc a CPLD implementation is better. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Setting Osc Frequencies
Hi Bruce, I for one would like to get the completed circuit seeing as I started the whole thing off and was just getting ready to maybe do a copy of the HP unit. Regards DonVK3YV. - Original Message - From: Dr Bruce Griffiths [EMAIL PROTECTED] To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Wednesday, April 11, 2007 4:34 PM Subject: Re: [time-nuts] Setting Osc Frequencies Hal Murray wrote: And Hal- what about the pcb layout for Bruce's 74CX version? Had time to look at it yet? It fell through the cracks when I got interested in something else. Is anybody really interested in that board? If so, please send me a reminder about the schematic. There have been lots of ideas kicked around recently. Is that still the right/best thing to build? I've used PCB Express, http://www.pcbexpress.com/ $125 for 10 boards, 2 layers, no solder mask, up to 9 sq inches $265 for solder mask and top silk screen. add $45 for silk on the bottom side Round up for shipping and taxes and whatever. Hal For a simple no frills linear phase detector using an AD9901 (available from Digikey in the 44pin PLCC package)in the ECL mode is a better bet. It only requires a couple of slow linear amplifiers to scale the output. No comparators are necessary for the inputs. Just a few diodes capacitors and resistors are required to terminate the input cables and protect the differential clock inputs. If you want more bells and whistles such as programmable input dividers etc a CPLD implementation is better. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] Sudden FMT
The next FMT will be Wednesday night April 11. 10:30 PM EDT 9:30 PM CDT 8:30 PM MDT 7:30 PM PDT 02:30 UTC The 80 meter run will be first, followed immediately by the 40 meter run and ending with the 160 meter run. 80 meter frequency will be near 355 Hz 40 meter frequency will be near 7055000 Hz 160 meter frequency will be near 1887000 Hz I don't really expect 160 will be useable by most of the group, but thought I would throw it in for the fun of it. Send your results and comments with in 22 hours to [EMAIL PROTECTED] Put Sudden FMT, your Call and frequency in Hz, in the subject line i.e.- Sudden FMT, K5CM, 1887000.23 Hz, 3550300.307 Hz, 7055034.7 Hz I will try to have the results posted within 48 hours after the test. http://pages.suddenlink.net/k5cm/ 73 Connie K5CM ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Setting Osc Frequencies
VK3YV wrote: Hi Bruce, I for one would like to get the completed circuit seeing as I started the whole thing off and was just getting ready to maybe do a copy of the HP unit. Regards DonVK3YV. Don AD9901 version attached. It needs another opamp to be added to allow the scale and offset to be adjusted. Some idea of the desired output voltage range and offset adjustment is needed. Vss = -5V. Vcc = 5V. Bruce AD9901PhaseDet.pdf Description: Adobe PDF document ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Oops - wrong URL for tvb plot!
In a message dated 4/10/2007 18:44:58 Pacific Daylight Time, [EMAIL PROTECTED] writes: Knowing or calculating the sample rate is useful: 15-20 samples/second seems OK for a 53132. But if you were to measure it you would come up with a more exact number. One way to do this is time the collection of 1000 samples. Hello Tom, (BTW - I don't like the reply feature of AOL, I can't keep your original post prefixed with etc. I think part of the reason is that the HTML stuff get's deleted by the server). Thanks for the info. I did do what you suggested, and I get 22.74 samples per second free-running over several hours. That makes the 0.1s Tau look nice. When using the timers' internal delay of 0.1s, I would expect the result to be slightly skewed, 1s + 50ns on average I would think since the measurement period has to be added as well? Presently, I am doing cross-correlation measurements using the 53132A: * Fury GPSDO (single AT-cut OCXO) against my FTS-4050 Cs * one Fury AT-cut GPSDO against our Fury Rubidium prototype (our secret project using a low-cost Russian Rb as the Fury OCXO) * Fury Rb against PRS-10 Rb, PRS-10 is GPS disciplined as well with ca. 7 hour time constant * PRS-10 Rb against FTS-4050 Cs. * Fury double-oven SC-cut unit against the best of all other oscillators (tbd) I do have some preliminary data which is very interesting: * The counter noise is dominant below 1s as you had mentioned. How can I do 0.001s measurements with such a noisy counter? * Our Fury Rubidium GPSDO prototype against the PRS-10 is the most stable combination, dropping below 1E-011 above 7s intervalls * The FTS-4050 is almost one magnitude more noisy than the Rubidiums at 100s intervalls. In fact it never catches the Rb's. I am a bit dissapointed by that. Of course it should be better long-term if GPS is completely turned off :) * All measurements get close to, or drop below 1E-012 at around 2000s intervalls (even the cheaper single-oven, AT-cut OCXO!). * The two Rubidiums drop below 1E-012 at around 1600 seconds. All measurements done using Ulrichs' Plotter ADEV utility. bye, Said ** See what's free at http://www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Oops - wrong URL for tvb plot!
The plotter utility, while it can read all sorts of suffixes etc, isn't happy with the comma. Comma removed, and it works perfectly (Ulrich, can you please fix this?) Said or Ulrich, an example of the code I use for this can be found in function hp53131() in source file: http://www.leapsecond.com/tools/adev1.c Note however that the 53131/132 can be configured for both EU and US style commas so Ulrich should either auto-detect which format the counter is outputting or allow the user to specify the format. /tvb ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Oops - wrong URL for tvb plot!
Tom Van Baak wrote: For fancier plotting I extract tau/adev pairs from either adev1 or Stable32 and make pretty log/log plots using Excel; MRTG, gnuplot, grace are alternatives. For those working in the *nix world, let me put in a plug for grace (plasma-gate.weizmann.ac.il/Grace/ ). It's a quite capable plotting tool, and what's really nice is that with the appropriate incantations it can operate in either interactive WYSIWYG mode or in batch mode from the command line (or a script). I've also figured out a way (with the help of an external perl script) to modify the basic plot parameters on the fly, so I can automagically generate customized plots without having to manually edit the grace configuation (that's my stable-stats program -- a bit of info is at http://www.febo.com/time-freq/tools). What's cool is that I can use the interactive mode to design a pretty chart, and then use the batch mode to automatically update it with new data. As a famously obnoxious computer columnist used to say, highly recommended. John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Comments on ADEV, MDEV, TDEV, etc
Tom Clark, K3IO wrote: I know it was mentioned earlier, but the bible on all these *DEV topics is the User Manual from Bill Wriley's STABLE32 (see [3]http://www.wriley.com/) and his various papers. Several of us (TvB, Rick me for 3) find that STABLE32 is one of the most useful software packages ever written; well worth the ~$400 it costs. Regards, Tom While I'm plugging things, I'll add my bit for STABLE32. It really is the definitive source for any sort of stability analysis. And, since I have to mention *nix in every post :-), I have it running reasonably well on my Linux system using the WINE emulator. There's one annoying hangup that results in crashes under certain circumstances, and I'm hoping the Wine guys will be able to resolve it, but until then, following the Doctor's advice: Well, don't do that, then works. By the way -- Ulrich's analysis program is also very good, and I've used it under Wine with good results as well. There's one problem with the Greek characters sometimes getting messed up in the display, but again that's fairly easy to live with. John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Oops - wrong URL for tvb plot!
John, I need your advise on the Gibraltar project. Is there a good time that we could speak on the phone? Rick W2GPS AMSAT LM2232 -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of John Ackermann N8UR Sent: Wednesday, April 11, 2007 8:39 AM To: Tom Van Baak; Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Oops - wrong URL for tvb plot! Tom Van Baak wrote: For fancier plotting I extract tau/adev pairs from either adev1 or Stable32 and make pretty log/log plots using Excel; MRTG, gnuplot, grace are alternatives. For those working in the *nix world, let me put in a plug for grace (plasma-gate.weizmann.ac.il/Grace/ ). It's a quite capable plotting tool, and what's really nice is that with the appropriate incantations it can operate in either interactive WYSIWYG mode or in batch mode from the command line (or a script). I've also figured out a way (with the help of an external perl script) to modify the basic plot parameters on the fly, so I can automagically generate customized plots without having to manually edit the grace configuation (that's my stable-stats program -- a bit of info is at http://www.febo.com/time-freq/tools). What's cool is that I can use the interactive mode to design a pretty chart, and then use the batch mode to automatically update it with new data. As a famously obnoxious computer columnist used to say, highly recommended. John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Comments on ADEV, MDEV, TDEV, etc
John, under all linuxes i have a very limited understanding of how to install and use Ubuntu. If you can tell me where to get a WINE for Ubuntu I will be able to peform some tests myself with running my software under the emu. 73 Ulrich, DF6JB P.S. I can do nothing else than to encourage the group to tell me about possible improvements of Plotter. I do not think it should replace STABLE32 but we amateurs need something to play around with without spending money on it, don't we? -Ursprüngliche Nachricht- Von: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Im Auftrag von John Ackermann N8UR Gesendet: Mittwoch, 11. April 2007 14:49 An: [EMAIL PROTECTED]; Discussion of precise time and frequency measurement Betreff: Re: [time-nuts] Comments on ADEV, MDEV, TDEV, etc Tom Clark, K3IO wrote: I know it was mentioned earlier, but the bible on all these *DEV topics is the User Manual from Bill Wriley's STABLE32 (see [3]http://www.wriley.com/) and his various papers. Several of us (TvB, Rick me for 3) find that STABLE32 is one of the most useful software packages ever written; well worth the ~$400 it costs. Regards, Tom While I'm plugging things, I'll add my bit for STABLE32. It really is the definitive source for any sort of stability analysis. And, since I have to mention *nix in every post :-), I have it running reasonably well on my Linux system using the WINE emulator. There's one annoying hangup that results in crashes under certain circumstances, and I'm hoping the Wine guys will be able to resolve it, but until then, following the Doctor's advice: Well, don't do that, then works. By the way -- Ulrich's analysis program is also very good, and I've used it under Wine with good results as well. There's one problem with the Greek characters sometimes getting messed up in the display, but again that's fairly easy to live with. John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi- bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Comments on ADEV, MDEV, TDEV, etc
Ulrich Bangert wrote: John, under all linuxes i have a very limited understanding of how to install and use Ubuntu. If you can tell me where to get a WINE for Ubuntu I will be able to peform some tests myself with running my software under the emu. All variations of linux have a package manager program. Some examples are yum, apt, aptitude, synaptic, yum-extender, kpackage, gpackage, yalp, fink... Ubuntu uses the synaptic package handler. It should be already installed, and ready to go. Here are some instructions: http://www.monkeyblog.org/ubuntu/installing/ -Chuck Harris ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Administrivia: Message Sizes
John, for sure I'll post the files on my site. Apologizes. Enrico On 11 Apr 2007, at 17:30 , John Ackermann N8UR wrote: I've been getting a lot of notices lately that messages are being rejected because they exceed the list's 128kb maximum size limit. Now that we have over 400 subscribers, I really need to enforce that limit; otherwise, the server gets bogged down (it's trying to blast out 400+ copies of that big message). The ideal thing is to post the large file at a web or ftp site, and just link to that location in your message. If you don't have public storage available, I'm sure several of us here would be happy to host files on their site; I certainly will (within reason). Thanks, John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts Enrico Rubiola professor of electronics web:http://rubiola.org e-mail: [EMAIL PROTECTED] FEMTO-ST Institute 32 av. de l'Observatoire 25044 Besancon, FRANCE voice: +33(0)381.853940 (E.Rubiola) voice: +33(0)381.853999 (switchboard) fax:+33(0)381.853998 ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Administrivia: Message Sizes
Thanks, Didier! John Didier Juges wrote: Anyone on this list is welcome use the upload section of my web site. It is intended for manuals, until I check them and move them to the formal Manual section, but since you can upload anything that will fit (25 GB please), you are welcome to use that for temporary storage as long as it is loosely related to the interests of this list, or the TekScope or hp_agilent_equipment mailing lists, which I participate in. If I need the room, I will simply delete the old stuff, but there is lots of space there, so you should be assured that whatever you upload will probably be there for at least a few weeks or months. Please do not upload sensitive information, or documents that could possibly irritate a big corporation with lots of copyright lawyers... If it is of more than passing interest and should be kept more permanently, send me an email and I will move the material in the Manual folder http://www.ko4bb.com/ham_radio/Manuals ftp.ko4bb.com login: manuals password: manuals To send a link in an email, you can either use ftp://ftp.ko4bb.com;, which requires the same login/password as above and provides you with an ftp interface, or simply http://www.ko4bb.com/~manuals/; which does not require login and presents an http interface, whichever you prefer. You are welcome to experiment. If you upload something and change your mind, the ftp interface will allow you to delete stuff in the upload folder. Be considerate of others please :-) Didier KO4BB John Ackermann N8UR wrote: I've been getting a lot of notices lately that messages are being rejected because they exceed the list's 128kb maximum size limit. Now that we have over 400 subscribers, I really need to enforce that limit; otherwise, the server gets bogged down (it's trying to blast out 400+ copies of that big message). The ideal thing is to post the large file at a web or ftp site, and just link to that location in your message. If you don't have public storage available, I'm sure several of us here would be happy to host files on their site; I certainly will (within reason). Thanks, John ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] time-nuts Digest, Vol 33, Issue 29
Tom Van Baak [EMAIL PROTECTED] wrote: If anyone has other favorite plotting methods, please let us know. Although I use and favor gnome as my desktop, I've been using kde's kst plotting package. It is not bad, which for me, discussing a software package, is an above average endorsement. There are some rough edges, for sure, but it draws nice plots, handles multiple data files and live file updates fairly well, and has some OK fitting and filtering capabilities. (It is pluggable, too -- one could imagine an adev plugin.) See the attached png for an example(1). The rest of my kit includes stable32 and a bunch of perl, awk and C++ code. I'd like to put a proper set of tools together out as a package some day. Incidentally, I've found that it is important to be quite careful with your floating point handling when representing a quantity of seconds with picosecond resolution in an IEEE 64-bit float. This is where exact float support or a big float package comes in handy. Some languages may support exact/big floats natively (some scheme implementations, nickel[sic]). For others, support is often in a library. Math::BigFloat does the trick for Perl. See the attached perl file, which does 5313x conversion without any loss of any precision. An explicit rational representation also works, but it is handy to have a library or language support to handle the arithmetic as it is tricky to get it both right and fast. For C++, boost's rational support is quite good (as is most everything in boost). -ch (1) The anomaly in the plot is something that hit all my gps receivers, including 2 Z3801a's, an m12+, and, as in the graph, an m12t. Odd, huh? hp5313x.pl Description: Binary data kst-eg_1.png Description: PNG image ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] time-nuts Digest, Vol 33, Issue 29
Incidentally, I've found that it is important to be quite careful with your floating point handling when representing a quantity of seconds with picosecond resolution in an IEEE 64-bit float. Can you give me an example of where you'd run into this? I ask because typically I think one normalizes incoming data so it doesn't matter if the raw values are seconds or picoseconds, and thus you get the same 54-bit precision either way, no? /tvb ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] Delay Line Discriminator article
I came across an old article on the Delay Line Discriminator for Phase Noise Measurements (Microwave Journal 1983). I don't think the theory has changed much since then :-) http://www.ko4bb.com/ham_radio/Manuals/3_GPS_Stuff/DelayLineDiscriminator.pdf Didier KO4BB ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Delay Line Discriminator article
Dear all, I have developed a theory of the delay line. Using the Laplace transform of the phase, mathematics is amazingly simple. Pick up the article no.6 on http://rubiola.org/journal-articles/readme.html Very best,. Enrico On 11 Apr 2007, at 20:19 , Didier Juges wrote: I came across an old article on the Delay Line Discriminator for Phase Noise Measurements (Microwave Journal 1983). I don't think the theory has changed much since then :-) http://www.ko4bb.com/ham_radio/Manuals/3_GPS_Stuff/ DelayLineDiscriminator.pdf Didier KO4BB ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts Enrico Rubiola professor of electronics web:http://rubiola.org e-mail: [EMAIL PROTECTED] FEMTO-ST Institute 32 av. de l'Observatoire 25044 Besancon, FRANCE voice: +33(0)381.853940 (E.Rubiola) voice: +33(0)381.853999 (switchboard) fax:+33(0)381.853998 ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Looking for Wavecrest Visi
well - that's my main reason I did the post - I wish I had Visi for Windows2K so I could do exactly that! I am trying to set up a Win98 machine with GPIB since I bought a quite old version of Visi from Wavecrest that runs only on Win98. I thought I remember from the manual that there's a whole set of nice SCPI commands. Can't you just send them by hand or code something up using the USB-GPIB board? /tvb ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Crossing International Date line causes F-22 Jet Problems
On 4/11/07, Brooke Clarke [EMAIL PROTECTED] wrote: If the computer program is in the millions of lines and had this bug, what other bugs does it have? Very similar to a bug in F-16 software that caused the fly-by-wire to roll the a/c inverted when it passed south of the equator. I believe that bug was caught in simulation testing, though. -- Margaret Stephanie Leber CCP, SCJP SCWCD [EMAIL PROTECTED] http://voicenet.com/~maggie AOPA 925383 -- Amateur Radio Station K3XS -- ARRL 39280 -- AMSAT 32844 The art of progress is to preserve order amid change and to preserve change amid order.-A.N.Whitehead ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Looking for Wavecrest Visi
I am trying to set up a Win98 machine with GPIB since I bought a quite old version of Visi from Wavecrest that runs only on Win98. Did you try using compatibility mode on WinXP to run that software? ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Looking for Wavecrest Visi
6a I used a 100k sample average which yields (IIRC) 200 femtosecond resolution in the 5370B, and for each run checked the min, max, and standard deviation statistics to make sure nothing goofy was going on Standard deviation for a run like that on my 5370B is typically 30 to 40ps. John 30-40 ps seems OK to me. But are you saying then that you get a measured value to 200 fs resolution but with +/- 30 ps standard deviation? This doesn't feel right at all. It seems to me if your sdev is +/- 30 ps it is incorrect to even write down the measured values to ps levels; and fs are out of the question. / ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Looking for Wavecrest Visi
In a message dated 4/11/2007 15:29:46 Pacific Daylight Time, [EMAIL PROTECTED] writes: I am trying to set up a Win98 machine with GPIB since I bought a quite old version of Visi from Wavecrest that runs only on Win98. Did you try using compatibility mode on WinXP to run that software? Hi, how do I do that, and still have the old software use the NI-488 drivers? thanks, Said ** See what's free at http://www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Looking for Wavecrest Visi
In a message dated 4/11/2007 14:22:14 Pacific Daylight Time, [EMAIL PROTECTED] writes: I thought I remember from the manual that there's a whole set of nice SCPI commands. Can't you just send them by hand or code something up using the USB-GPIB board? /tvb If only I had the time... Coding is probably not too tough, but debugging could take very long. Also, Visi has their patented tail-fit jitter algorithm which gives you the left and right RMS random jitter when the signal has deterministic jitter on it. Don't think other instruments can do that. Very useful for DDS design where spurs (read deterministic jitter) comes with the territory. What bugs me is that I paid for that Visi software, and cannot use it. It does what I need it to do... They want over $6K for the newer versions of Visi. BTW: someone bought the Wavecrest DTS-2070 on Ebay. Maybe they have the time to code something up? bye, Said ** See what's free at http://www.aol.com. ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] GPS: ADEV or MDEV?
Hal Murray wrote: Surely it would be much simpler (in principle at least) to just to add sufficient Gaussian phase noise to the GPS receiver clock so that potential coherence problems are virtually eliminated. It doesn't look reasonable to me, but I'm not good at this sort of math. The clock is, say, 40 MHz. That's 25 ns, so the output jitter will be 25 ns p-p. If you are at the top of a hanging bridge, you have to add enough noise to hide a 12.5 ns offset. Will a typical GPS receiver still work with that much trash on its clock signal? What sort of noise spectrum would you use? Hal The noise only really needs to be added to the PPS positioning algorithm/hardware. In principle (if you can get at the firmware) it would be possible to implement noise shaping using a sigma delta modulator (possibly with added noise dithering to break up idle patterns - like hanging bridges) so that the short term PPS positioning noise increases but the average position is more stable. This may be useful when a long time constant PLL is used to discipline an oscillator with the PPS output of the receiver. Bruce ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] flaot representation of phase measurements (was Re: time-nuts Digest, Vol 33, Issue 29)
Incidentally, I've found that it is important to be quite careful with your floating point handling when representing a quantity of seconds with picosecond resolution in an IEEE 64-bit float. Can you give me an example of where you'd run into this? I ask because typically I think one normalizes incoming data so it doesn't matter if the raw values are seconds or picoseconds, and thus you get the same 54-bit precision either way, no? /tvb There are 52 represented bits of significand (mantissa) in an IEEE 754 double, with one bit implied, for a total of 53 bits. But the exact number of bits isn't relevant -- no matter how many bits are used in the significand, given a particular base, there are some rational values that cannot be represented exactly. IEEE 754 floats use base 2. The exact (ha ha!) restriction is that the denominator has to be a power of 2. As 1 is 2^0, representing integer quantities within a certain (and useful) range (but well short of the minimum and maximum values) happens exactly in the IEEE floating point representation. The implication is that a double quantity of picoseconds may be exact, whereas the equivalent quantity represented as a double of whole + fractional seconds may not be, because 1E-12 is not a power of 2. Of course, if your quantity of integer picoseconds gets too large you will run into the other end of inexactness. But, let's get back to the 53132. Here's a real example where the exactness issue is evident (assuming Outlook doesn't mangle the lines too badly): [EMAIL PROTECTED]:~/src/freqstd$ cat /tmp/eg 11763407150.300,072,693,8 s 11763407160.300,072,699,5 s 11763407170.300,072,700,5 s 11763407180.300,072,706,0 s 11763407190.300,072,705,5 s 11763407200.300,072,710,5 s 11763407210.300,072,710,4 s 11763407220.300,072,714,4 s 11763407230.300,072,685,7 s 11763407240.300,072,684,3 s [EMAIL PROTECTED]:~/src/freqstd$ ./hp5313x-r116.pl /tmp/eg 11763407153.000726938001e-01 11763407163.000726994998e-01 11763407173.000727005001e-01 11763407183.000727060002e-01 11763407193.000727054998e-01 11763407203.000727105001e-01 11763407213.000727104000e-01 11763407223.000727144000e-01 11763407233.000726857001e-01 11763407243.000726843000e-01 [EMAIL PROTECTED]:~/src/freqstd$ ./hp5313x.pl /tmp/eg 11763407150.3000726938 11763407160.3000726995 11763407170.3000727005 11763407180.300072706 11763407190.3000727055 11763407200.3000727105 11763407210.3000727104 11763407220.3000727144 11763407230.3000726857 11763407240.3000726843 [EMAIL PROTECTED]:~/src/freqstd$ /tmp/eg is the raw data from a 51312 serial port prefixed with time_t timestamps. ./hp5313x-r116.pl is an earlier version of my conversion script that reads the TI values as IEEE doubles, scales them according to the suffix using IEEE double arithmetic, and prints them likewise. As you can see the values aren't exact -- and this is multiplying by (an exactly represented) 1.0. ./hp5313x.pl uses big floats. The values are read exactly, multiply exactly, and printed exactly. Certainly we can argue if/when this matters -- it does not in many cases, e.g., calculating adev(*).I particularly care here as I archive this (lightly) processed data; I want these simple transforms I do early on be correct and exact. -ch (*) It would also be bloody slow not to use IEEE doubles and hardware support. ___ time-nuts mailing list [EMAIL PROTECTED] https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
