Re: [time-nuts] New ± 1 sec in 100 days mech clock
There's a great series of videos from a clockmaker on youtube and his own site: http://clickspring.weebly.com/ These are probably the best produced how-to videos I've seen on youtube on any subject. Highly recommended. Matt On Wed, Apr 22, 2015 at 3:57 PM, Bob Camp kb...@n1k.org wrote: Hi In some ways this is like: I can buy tubes of paint and some brushes down at Hobby Lobby. That’s what I need to paint the next Mona Lisa. While that’s all quite true, it’s not the whole story :) There’s an enormous amount of training and experience that goes into fitting this sort of thing up. There is even a certain amount of “art” that goes beyond simple training. Not all watch/clock makers are up to this sort of thing. Highly skilled people have been trying to do this kind of clock for a *long* time ….It’s not just an assembly process. Indeed I’d love to see the details of how they did the design. There are some basic challenges that they (obviously) addressed very well. Even with a good description of what they did and a pile of parts, you are still only (maybe) 10% of the way to a duplicate. Note: I’m *not* claiming I am any good at clock making. I’ve simply seen a lot of this sort of work done over the years. Bob On Apr 22, 2015, at 10:03 AM, Dan Kemppainen d...@irtelemetrics.com wrote: Hi, In all reality, achieving these results without decades of experience is probably unlikely. That said, are the specific plans available or published anywhere? Is is possible that someone willing to build and tinker could make a 'functional' copy of this unit? I would guess that not all of the parts need extreme tolerances. But even then many mills are holding positioning tolerances well under .001, with tool deflections of .0001 or under (if run and maintained properly, that is). My 'list' includes a mechanical clock build. And this one would be a dandy to try to build! In any case, the clock is still interesting to read about! It's great that some of you are lucky enough to get to see it! :) Dan On 4/21/2015 12:00 PM, time-nuts-requ...@febo.com wrote: You could always use the traditional method of piercing saw and files. Thinking about it I suppose files were the original milling machine. Be aware that the horological approach is different from the engineering approach and there are numerous traps waiting for the unwary. Harrison and Martin's clock B have remarkable performance but could still be improved by using multiple pendulums to overcome the noise effects for example a two pendulum clock is performing within 1 second in six months (so far) so I will have to get the hacksaw out for the three pendulum version - or is it back to the GPSDO. Peter ___ 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] GPS PPS smoothing article
Interesting work. They measured the before and after signals with 2 very different oscilloscopes one with 100 MHz BW and one with 500 MHz, which they shouldn't trust.. I guess they only had 2 2-channel scopes in their lab. Matt On Sun, Apr 11, 2010 at 5:27 AM, Magnus Danielson mag...@rubidium.dyndns.org wrote: Fellow time-nuts, Another article about GPS PPS tracking. Their twist to it has been to lower the PPS jitter, not to create a locked 10 MHz clock. I though it may be useful for someone at least: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.129.8625rep=rep1type=pdf Cheers, Magnus ___ 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] CPLDs for clock dividers
Thanks to everyone for their advice. I bought a CoolRunner II development board (only $39!) and will let you know how it goes. Matt On Wed, Feb 3, 2010 at 10:59 AM, Matt Ettus boysc...@gmail.com wrote: Does anyone have any experience using CPLDs for very low phase noise dividers? You can get an XC9536XL from Xilinx for around $1, and I thought it would make a good divide by 2 through 10 device. Matt ___ 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] CPLDs for clock dividers
Does anyone have any experience using CPLDs for very low phase noise dividers? You can get an XC9536XL from Xilinx for around $1, and I thought it would make a good divide by 2 through 10 device. Matt ___ 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] HP E2050A LAN/HPIB Gateway
You can get it from our anonymous svn repo by doing this: svn co https://ettus.devguard.com/svn/public Matt On Wed, Sep 2, 2009 at 12:27 AM, Chad Simpsonanalogaficion...@gmail.com wrote: Matt, I would be very interested in the python code. I got a good deal on the E2050A, and though I haven't set it up yet, I imagine it works the same as the E5810A, just without the DHCP and web config features. Adrian, I don't have the full manual, but I emailed you the Installation and Configuration guide pdf. If anyone else would like a copy, just let me know... - Chad. On Tue, Sep 1, 2009 at 3:53 PM, Matt Ettus boysc...@gmail.com wrote: We don't use the NI stuff at all. We have our own SCPI-over-GPIB-over-VXI11-over-TCP/IP code all in python, based around some code off of sourceforge. We use it exclusively with the E5810A which is great. It also works with the Prologix USB device, and if you have the right magic kernel incantations the GPIB-USB-B from NI. It would probably also work with the GPIB-ethernet gateway from ICS electronics which is also VXI11 like the E5810A, but about 25% cheaper. Matt On Tue, Sep 1, 2009 at 12:32 PM, Lester Veenstram0...@veenstras.com wrote: Matt: You caught my interest with the Python. Do you have a Python interface to the NI GPIB drivers, or some other way to bet from Python to GPIB. I have been looking but not found such a beast, and was contemplating writing it in C the hard way. But I suspect some one has been there before me. ??? 73 Les Lester B Veenstra MØYCM K1YCM les...@veenstras.com m0...@veenstras.com k1...@veenstras.com US Postal Address: PSC 45 Box 781 APO AE 09468 USA UK Postal Address: Dawn Cottage Norwood, Harrogate HG3 1SD, UK Telephones: Office: +44-(0)1423-846-385 Home: +44-(0)1943-880-963 Guam Cell: +1-671-788-5654 UK Cell: +44-(0)7716-298-224 US Cell: +1-240-425-7335 Jamaica: +1-876-352-7504 This e-mail and any documents attached hereto contain confidential or privileged information. The information is intended to be for use only by the individual or entity to whom they are addressed. If you are not the intended recipient or the person responsible for delivering the e-mail to the intended recipient, be aware that any disclosure, copying, distribution or use of the contents of this e-mail or any documents attached hereto is prohibited. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Matt Ettus Sent: Tuesday, September 01, 2009 7:14 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] HP E2050A LAN/HPIB Gateway have full python code for . ___ 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] HP E2050A LAN/HPIB Gateway
I'm not sure if the programming is the same, but we use a couple of the E5810A and love it. We have full python code for using it if that is of use. Matt On Tue, Sep 1, 2009 at 10:32 AM, Adrianrfn...@arcor.de wrote: Ulrich, thanks for your reply. I have installed the I/O libraries suite 14.0 that supports the E2050A. However, I don't get any communication with the unit, no matter if I connet it to my LAN or directly with a crossover cable. I think a manual would probably do the trick. Adrian Ulrich Bangert schrieb: Adrian, not sure whether you can reach your aim completely without a manual. However installing the AGILENT I/O Libraries should bring you a big step forward. Having installed the software it should recognize the E5020A and the GPIB devices connected to it, so that some basic communication tests should be possible from within the GUI (i.e. without any programming). After basic functionality tests you should be able to talk to your instruments through the I/O Libraries with any software that knows how to make use of VISA functionality, for example my EZGPIB utility (but of course there are others too). Best regards Ulrich -Ursprungliche Nachricht- Von: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] Im Auftrag von Adrian Gesendet: Dienstag, 1. September 2009 15:48 An: time-nuts@febo.com Betreff: [time-nuts] HP E2050A LAN/HPIB Gateway Hi, hope it's not considered too far off-topic. (Actually, I'm trying to control some counters etc. of my time and frequncy rack through the E2050A.) I just don't get it working. I have the 4-page 'overview' but couldn't find any other information. Anyone got a manual for me? Regards, Adrian ___ 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] HP E2050A LAN/HPIB Gateway
We don't use the NI stuff at all. We have our own SCPI-over-GPIB-over-VXI11-over-TCP/IP code all in python, based around some code off of sourceforge. We use it exclusively with the E5810A which is great. It also works with the Prologix USB device, and if you have the right magic kernel incantations the GPIB-USB-B from NI. It would probably also work with the GPIB-ethernet gateway from ICS electronics which is also VXI11 like the E5810A, but about 25% cheaper. Matt On Tue, Sep 1, 2009 at 12:32 PM, Lester Veenstram0...@veenstras.com wrote: Matt: You caught my interest with the Python. Do you have a Python interface to the NI GPIB drivers, or some other way to bet from Python to GPIB. I have been looking but not found such a beast, and was contemplating writing it in C the hard way. But I suspect some one has been there before me. ??? 73 Les Lester B Veenstra MØYCM K1YCM les...@veenstras.com m0...@veenstras.com k1...@veenstras.com US Postal Address: PSC 45 Box 781 APO AE 09468 USA UK Postal Address: Dawn Cottage Norwood, Harrogate HG3 1SD, UK Telephones: Office: +44-(0)1423-846-385 Home: +44-(0)1943-880-963 Guam Cell: +1-671-788-5654 UK Cell: +44-(0)7716-298-224 US Cell: +1-240-425-7335 Jamaica: +1-876-352-7504 This e-mail and any documents attached hereto contain confidential or privileged information. The information is intended to be for use only by the individual or entity to whom they are addressed. If you are not the intended recipient or the person responsible for delivering the e-mail to the intended recipient, be aware that any disclosure, copying, distribution or use of the contents of this e-mail or any documents attached hereto is prohibited. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Matt Ettus Sent: Tuesday, September 01, 2009 7:14 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] HP E2050A LAN/HPIB Gateway have full python code for . ___ 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] Multiple Voltage monitoring
On Thu, Jul 30, 2009 at 10:17 PM, Tom Van Baakt...@leapsecond.com wrote: Does anyone have a good solution for monitoring 4-8 different voltages at the same time? I only need a sample rate around 1-2 Hz, but would need GPIB, serial, or ethernet support with protocol documentation. Any help identifying a solution other than 8 voltmeters would be much appreciated. Thanks, Matt Check out http://www.labjack.com /tvb Thanks to everyone for the great suggestions, and to Tom in particular for the LabJack suggestion. I hadn't heard of many of those companies. In the end, I decided to go with the LabJack UE9, which is inexpensive, flexible, and has an ethernet interface. LabJack seems to be very supportive of open source, their protocols are all open, and they even provide Linux, Mac, and Python drivers! Also interesting, check out: http://cloud.labjack.com This is their data acquisition server service... Very cool idea. Matt ___ 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] Multiple Voltage monitoring
Does anyone have a good solution for monitoring 4-8 different voltages at the same time? I only need a sample rate around 1-2 Hz, but would need GPIB, serial, or ethernet support with protocol documentation. Any help identifying a solution other than 8 voltmeters would be much appreciated. Thanks, Matt ___ 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] Multiple Voltage monitoring
DC, 0 to 6V, 10mV or better resolution. Thanks, Matt On Thu, Jul 30, 2009 at 9:08 PM, WB6BNQwb6...@cox.net wrote: Hi Matt, 1. Is the voltage AC or DC ? 2. What is the voltage range ? 3. What kind of resolution ? BillWB6BNQ Matt Ettus wrote: Does anyone have a good solution for monitoring 4-8 different voltages at the same time? I only need a sample rate around 1-2 Hz, but would need GPIB, serial, or ethernet support with protocol documentation. Any help identifying a solution other than 8 voltmeters would be much appreciated. Thanks, Matt ___ 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] Multiple Voltage monitoring
I've actually got some of their ethernet devices. The problem is that the drivers are all closed. They give no info on how to talk to them without LabView. Matt On Thu, Jul 30, 2009 at 9:34 PM, John Milesjmi...@pop.net wrote: National Instruments has been getting aggressive with their pricing lately: e.g., http://zone.ni.com/devzone/cda/tut/p/id/8675 . I was actually toying with the idea of getting into the DAQ business a few months ago, but I changed my mind in a hurry when I saw their ads. -- john, KE5FX -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com]on Behalf Of Matt Ettus Sent: Thursday, July 30, 2009 9:19 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Multiple Voltage monitoring DC, 0 to 6V, 10mV or better resolution. Thanks, Matt On Thu, Jul 30, 2009 at 9:08 PM, WB6BNQwb6...@cox.net wrote: Hi Matt, 1. Is the voltage AC or DC ? 2. What is the voltage range ? 3. What kind of resolution ? BillWB6BNQ Matt Ettus wrote: Does anyone have a good solution for monitoring 4-8 different voltages at the same time? I only need a sample rate around 1-2 Hz, but would need GPIB, serial, or ethernet support with protocol documentation. Any help identifying a solution other than 8 voltmeters would be much appreciated. Thanks, Matt ___ 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] NI WLS/ENET-92xx data acquisition
Has anyone used the National Instruments WLS-92xx or ENET-92xx ethernet- and wireless-based data acquisition systems? Have you been able to use them without using NI software? Is their protocol documented anywhere? It's an interesting product family, with 802.11 or ethernet interfaces, you can get 4 channels of many kinds of data acquisition. The 9211 for thermocouples is the most interesting to me right now. I need to measure temperature at a lot of points in an oven. Thanks, Matt ___ 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] HP 4352A/B with different signal generator
Does anyone know if it is possible to use the HP4352A/B VCO/PLL analyzers with signal generators other than the 8665A? What is involved? I have a sig gen which is plenty good, so buying an 8665 just to go with a 4352 (which you can now get for about $1K) seems like a waste. Thanks, Matt ___ 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] HP 4352A/B with different signal generator
There's a 4352B on ebay for a $1K start bid, but there's a reserve. There's a 4352A for $1999 Buy it Now with an Or Best Offer option. In general, this is an absolutely great time to get modern test equipment at very low cost. With the economy down, everybody wants to get rid of inventory. I just got a like-new R+S SMATE200A (Dual IQ signal generator up to 6 GHz) for $8K, even though the new price is still $65K. I think I could have gotten it for less if I had tried, since it was right before the end of the year. On the subject of the alternate sig gen with a 4352, do you need to just tune it to some frequency offset away from the signal you are measuring? Does the offset change during the measurement? If it changes during the measurement, some form of automation would be necessary. Thanks, Matt On Sat, Jan 31, 2009 at 1:32 PM, Brooke Clarke bro...@pacific.net wrote: Hi Matt: Where can I get one for that price? The Sig Gen phase noise is the driving spec since it needs to be better than the phase noise of the VCO you are measuring. Have Fun, Brooke Clarke http://www.prc68.com Matt Ettus wrote: Does anyone know if it is possible to use the HP4352A/B VCO/PLL analyzers with signal generators other than the 8665A? What is involved? I have a sig gen which is plenty good, so buying an 8665 just to go with a 4352 (which you can now get for about $1K) seems like a waste. Thanks, Matt ___ 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] Common sky pps errors for any GPSDOs?
I am working with someone who needs to have time synchronized reception of signals in various locations which are separated by less than 100 km. This is a situation similar to VLBI, but since the distances are shorter, the center frequencies are lower, and the integration times are much shorter, we probably don't need a Hydrogen Maser, and the application can't afford one. The real question is whether we can get away with a GPS disciplined OCXO or whether we would need to use a Rubidium. Does anyone have any data on the relative frequency and/or phase errors of the 10 MHz reference out, and relative PPS time errors of any commonly available GPSDOs? Absolute error to UTC and true 10 MHz don't really matter, as long as both devices have the same error. Just data comparing 2 units with antennas right next to each other would probably be fine. The other concern, of course, is that even if both units were very close, they will be exposed to slightly different environmental conditions (different A/C settings, different cycling times, etc.). Are there any good papers discussing this subject? Any data out there? Said -- have you measured this sort of thing on the Fury? Thanks, Matt ___ 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] Common sky pps errors for any GPSDOs?
On Mon, Jan 5, 2009 at 12:13 PM, Lux, James P james.p@jpl.nasa.gov wrote: -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Matt Ettus Sent: Monday, January 05, 2009 11:31 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Common sky pps errors for any GPSDOs? I am working with someone who needs to have time synchronized reception of signals in various locations which are separated by less than 100 km. This is a situation similar to VLBI, but since the distances are shorter, the center frequencies are lower, and the integration times are much shorter, we probably don't need a Hydrogen Maser, and the application can't afford one. The real question is whether we can get away with a GPS disciplined OCXO or whether we would need to use a Rubidium. Does anyone have any data on the relative frequency and/or phase errors of the 10 MHz reference out, and relative PPS time errors of any commonly available GPSDOs? Isn't that just the Allan Deviation data? Symmetricom has datasheets on their website for their various modules. They have a GPS discplined quartz oscillator in several flavors. http://www.symmetricom.com/media/files/downloads/product-datasheets/ds%20XLi%20Options%202.pdf I don't think Allan Deviation is the right measure. First, standard Allan dev numbers won't take environmental differences into account. Also, isn't Allan Dev measured vs. a better reference? Something else to consider is doing post processing.. Use a nice quiet 10MHz oscillator for your source/sampling clock, and record the 1PPS from the GPS receiver as well as your unknown, then figure out after the fact what the oscillator was doing. Unfortunately, post processing isn't possible in this app, since it is a real-time communications application. Thanks, Matt ___ 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] Common sky pps errors for any GPSDOs?
On Mon, Jan 5, 2009 at 1:54 PM, Bruce Griffiths bruce.griffi...@xtra.co.nz wrote: If the application is somewhat analogous to VLBI, then the maximum (uncorrectable ie random) allowable carrier frequency phase errors between receivers depends on the integration time. Maximum integration times for VLBI are typically 10,000 sec or less, with corresponding relative ADEV (after correction for drift etc) on the order of 1E-14 (or better) @ 10,000 sec for a carrier frequency of a few GHz. What is the integration time in your application? We are trying to receive data which is modulated at rates which vary, but are in the 100 Hz to 100 kHz range, so the integration times are very short, all below 10ms. What is the carrier frequency? 30 MHz and below for now, but we'd like to be able to go as high as 500 MHz or so. For short integration times most rubidium standards are much noisier than a good OCXO. GPS carrier phase techniques will allow lower noise comparisons of LO phase differences than a GPS derived PPS based system. Don't the Rb standards end up disciplining an OCXO so you get the benefit of the crystal at the shortest integration times? Thanks, Matt ___ 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] Common sky pps errors for any GPSDOs?
On Mon, Jan 5, 2009 at 2:56 PM, Lux, James P james.p@jpl.nasa.gov wrote: -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Matt Ettus Sent: Monday, January 05, 2009 2:28 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Common sky pps errors for any GPSDOs? On Mon, Jan 5, 2009 at 12:13 PM, Lux, James P james.p@jpl.nasa.gov wrote: -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Matt Ettus Sent: Monday, January 05, 2009 11:31 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Common sky pps errors for any GPSDOs? I am working with someone who needs to have time synchronized reception of signals in various locations which are separated by less than 100 km. This is a situation similar to VLBI, but since the distances are shorter, the center frequencies are lower, and the integration times are much shorter, we probably don't need a Hydrogen Maser, and the application can't afford one. The real question is whether we can get away with a GPS disciplined OCXO or whether we would need to use a Rubidium. Does anyone have any data on the relative frequency and/or phase errors of the 10 MHz reference out, and relative PPS time errors of any commonly available GPSDOs? Isn't that just the Allan Deviation data? Symmetricom has datasheets on their website for their various modules. They have a GPS discplined quartz oscillator in several flavors. http://www.symmetricom.com/media/files/downloads/product-datasheets/ds %20XLi%20Options%202.pdf I don't think Allan Deviation is the right measure. First, standard Allan dev numbers won't take environmental differences into account. Also, isn't Allan Dev measured vs. a better reference? Environmental differences, as in the environment of the box? Or the propagation path? For the box, the short term is going to be dominated by the OCXO, isn't it? So it's relatively environment immune. Allan Dev is the box against itself,in the adjacent time slice, but wouldn't that be pretty similar to a box against an identical box, because the noise is assumed to be uncorrelated from time slice to time slice. Something else to consider is doing post processing.. Use a nice quiet 10MHz oscillator for your source/sampling clock, and record the 1PPS from the GPS receiver as well as your unknown, then figure out after the fact what the oscillator was doing. Unfortunately, post processing isn't possible in this app, since it is a real-time communications application. OH.. This is like doing a distributed phased array for EME (or, as N5BF wants to do, EVE) Yes, a very similar application. On the basis of your other mail a few minutes later, you're looking at very short integration time (e.g. 10ms), so wouldn't phase noise be your more appropriate thing to look at, and for that, you're almost certainly looking at the basic properties of the quartz oscillator. Well, basically, I need to be able to coherently add signals from multiple locations without first looking at those signals to determine what the phase error is. OTOH, if you're trying to a phased uplink sort of thing, then you are concerned about longer time intervals (e.g. you want the relative phases of Tx1 and Tx2 to be constant over intervals of seconds) Yes, we would need the relative phase to be constant over time scales up through about a second or two. Matt ___ 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] Common sky pps errors for any GPSDOs?
On Mon, Jan 5, 2009 at 3:02 PM, Bruce Griffiths bruce.griffi...@xtra.co.nz wrote: Matt Matt Ettus wrote: On Mon, Jan 5, 2009 at 1:54 PM, Bruce Griffiths bruce.griffi...@xtra.co.nz wrote: If the application is somewhat analogous to VLBI, then the maximum (uncorrectable ie random) allowable carrier frequency phase errors between receivers depends on the integration time. Maximum integration times for VLBI are typically 10,000 sec or less, with corresponding relative ADEV (after correction for drift etc) on the order of 1E-14 (or better) @ 10,000 sec for a carrier frequency of a few GHz. What is the integration time in your application? We are trying to receive data which is modulated at rates which vary, but are in the 100 Hz to 100 kHz range, so the integration times are very short, all below 10ms. What is the carrier frequency? 30 MHz and below for now, but we'd like to be able to go as high as 500 MHz or so. What's your tolerance for phase variations between a pair of LOs? Its on the order of 50 degrees or so for VLBI. At 500MHz this corresponds to about 140ps. The corresponding relative ADEV is around 1E-8 @ tau = 10ms. Almost any good crystal oscillator can achieve this. As you said, our ADEV requirements are pretty loose and could be met by any decent crystal. But Said just told us that he sees about 25ns difference between units, which is about 180 times worse than 140 ps. In VLBI I think that they can deal with an unknown phase error between the two LOs as long as that phase error remains relatively constant over the period of integration. That is why they care about ADEV. They just correlate the two signals, and subtract out that constant phase error. My problem is that we can't just do that in this application. We need to know that phase error a priori. Matt ___ 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] Common sky pps errors for any GPSDOs?
On Mon, Jan 5, 2009 at 9:27 PM, saidj...@aol.com wrote: Hi Matt, having 140ps matching of the 1PPS between units is the equivalent of knowing your antenna position to within ~0.14 feet total error max. Thats less than one inch error per antenna! That makes it sound a lot more difficult than it really is. The vast majority of the error in GPS is systematic, such that two GPS systems with antennas near each other should have highly correlated error. This is the basis of differential GPS. It doesn't matter if the absolute error is hundreds of feet, as long as both devices have the same error. I spent a couple of years nearly a decade ago doing differential GPS for steering heavy equipment. You can get sub-centimeter errors over baselines in the tens of km. Again, this is relative error. Matt ___ 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] Common sky pps errors for any GPSDOs?
On Mon, Jan 5, 2009 at 10:59 PM, saidj...@aol.com wrote: Hi Matt, I must admit I don't fully understand your requirements. Are you looking for correlation between errors, or absolute UTC accuracy, or short term jitter/wander? If you have two systems with self-surveyed antenna positions, you will likely have 1 - 10 feet of antenna height error in the self survey on the Motorola timing receivers (typically). This position-hold error in itself will give you much more than 140ps error (offset, drift, wander) between the units as satellites fade in and out of solution, even if the units are sitting right next to each other and are seeing the same systemic GPS errors. For example, let's say both units share the same antenna, and after auto-survey one reports it's height as 10 feet MSL, the other unit as 15 feet MSL (M12M's have easily more than 5 feet height error after self-survey). So if you now compare the outputs of the units, satellites directly overhead could cause a 5 feet, or ~5ns error, while sats at the horizon will not be affected by the height error, but rather the long/lat errors (which are much smaller). So unless you have a perfectly surveyed antenna position stored in the two receivers (to within 1 foot) you will get GPS systemic errors as well as timing errors due to position error - especially due to antenna height errors. When we say units typically have 25ns unit-to-unit variation on the 1PPS on un-calibrated units, then I believe most of this is caused by the auto-survey position errors of the GPS receiver. One could get much better performance by manually entering the exact position-hold position of the antenna, and then calibrating for antenna cable delay (in 1ns steps). This seems to yield down to 2ns performance as reported by Motorola/Synergy/NIST with careful calibration, and using a proper GPS timing antenna with multipath choke-ring etc. But again, this requires a perfectly surveyed antenna position, as well as offset correction due to antenna cable length delay. There are also antenna cable length variations due to ambient temperature changes :) Bruce and others had discussed these errors not too long ago. 140ps error (or 70ps per GPSDO unit) may be possible on a long antenna cable just due to temperature changes on the cable.. Lastly, our units seem to have a residual PLL tracking noise floor of down to 1.9ns rms when using a good double oven OCXO as can be seen on the unit running in Mexico using a properly surveyed antenna position: _http://resco.ucol.mx/Fury/gpsstat.htm_ (http://resco.ucol.mx/Fury/gpsstat.htm) Getting 140ps matching offset error between two different units' 1PPS outputs may be tough to achieve. I see what you are saying here. I guess that it will be necessary to have some way to calibrate out the long term phase variations from the received signals just like in VLBI. I think it would be interesting to see the raw data from a time interval counter on the PPS of two identical GPSDOs sharing an antenna. If anyone has that sort of data, maybe over a day or two, I'd love to get a copy. Thanks, Matt ___ 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] Mini Circuits Power Meter PWR-6G+
I just got a Mini Circuits power meter, the PWR-6G+, which is good to 6 GHz, -30 dBm to +20dBm. It hooks up by USB and is only $695. Very cool device, and quite accurate from what I can tell. It's a nice small package, just a sensor head with USB cable. My only complaint is that I can't find Linux drivers for it. Looks like they use this chip: http://www.delcom-eng.com/DelcomCD/USBChips/USBChips.htm So maybe it wouldn't be hard to talk to it. Matt ___ 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] pps vs. 10 MHz timing
On my Oscilloquartz GPSDO, the 10 MHz output goes low at very close to the same time as the 1 PPS output goes high. On my Fury, the 10 MHz sine wave is just dropping off of its max high voltage as the 1 PPS goes high. The 10 MHz CMOS output goes high just shortly before the 1 PPS. What do other GPSDOs do? Clearly, any device trying to latch the 1 PPS signal using the 10 MHz clock will need to choose which clock edge to use, depending on which type of GPSDO is used. How is this normally handled? Also, I noticed that the TADD-1 has some weird distortion of a 10 MHz sine wave. It turns it into a sort of a 3 valued square wave. Essentially, it stops and dwells at the midpoint for a while instead of making a sharp transition. I think this would be bad if that dwell point is close to the threshold for the receiving device. Has anyone else noticed this? Thanks, Matt ___ 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] New Prologix GPIB-LAN Controller
On Tue, Aug 5, 2008 at 10:38 AM, Prologix [EMAIL PROTECTED] wrote: Hello, Prologix is happy to announce its newest product - GPIB-LAN Controller. Will there be VXI-11 support? The ICS 8065 and Agilent E5810A both support it, along with most of the new test equipment that talks ethernet. It would be nice not to have to rewrite apps. Matt ___ 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] Test equipment-level phase noise PLLs
In looking into extremely low phase noise synthesizers, I have come across the new HMC700LP4 chip from hittite, which seems to have the best figure of merit I have found, -227 dBm/Hz. That gives you -107dBc/Hz at 20 kHz offset at 6 GHz according to the datasheets. That sounds amazingly good, but my R+S signal generator does better. Do they use a different sort of architecture? Do they not use conventional dividers? Some other sort of phase detector? Thanks, Matt ___ 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] Prologix VRBOOT error
I just wanted to let everyone know that with the help of a firmware upgrade and some great support from Abdul, we no longer have any problems with the Prologix GPIB interface. Not having to rebuild GPIB drivers every time the kernel gets upgraded is a huge win for us. Thanks, Matt On Wed, Jun 4, 2008 at 6:50 AM, Prologix [EMAIL PROTECTED] wrote: Matt, We are testing a fix. I'll be in touch soon. Regards, Abdul -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Matt Ettus Sent: Wednesday, June 04, 2008 12:40 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Prologix VRBOOT error On Tue, Jun 3, 2008 at 5:31 PM, Prologix [EMAIL PROTECTED] wrote: Short version: Connect USB cable before connecting GPIB, and leave USB connected and powered. That isn't realistic for my setup. Long version: On startup, if one of the MCU I/O lines is pulled low, the controller will enter firmware update mode. As it happens, this I/O line is also one of the GPIB bus signals. Some instruments seem to have stronger pull-down on the bus lines than others. The controller may enter firmware update mode, if the USB cable is plugged in while the controller is connected to such an instrument. Since the pull-down is passive, this behavior could happen even if the instrument is powered down when connecting USB. Honestly, this sounds like a serious design flaw to me. I have 5 GPIB instruments, and 3 of them cause this behavior. If 3 pieces of test equipment from 3 different manufacturers cause this behavior, it must be pretty common. Matt ___ 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] low-g OCXO GPSDO
A normal OCXO would drift significantly when being turned around in any direction. I've actually been wondering about what physical mechanism that causes this. I could understand how it could cause a phase shift, but I can't envision the cause of frequency shift. Does anyone know? Matt ___ 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] Prologix VRBOOT error
On Tue, Jun 3, 2008 at 5:31 PM, Prologix [EMAIL PROTECTED] wrote: Short version: Connect USB cable before connecting GPIB, and leave USB connected and powered. That isn't realistic for my setup. Long version: On startup, if one of the MCU I/O lines is pulled low, the controller will enter firmware update mode. As it happens, this I/O line is also one of the GPIB bus signals. Some instruments seem to have stronger pull-down on the bus lines than others. The controller may enter firmware update mode, if the USB cable is plugged in while the controller is connected to such an instrument. Since the pull-down is passive, this behavior could happen even if the instrument is powered down when connecting USB. Honestly, this sounds like a serious design flaw to me. I have 5 GPIB instruments, and 3 of them cause this behavior. If 3 pieces of test equipment from 3 different manufacturers cause this behavior, it must be pretty common. Matt ___ 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] Prologix VRBOOT error
On Tue, Jun 3, 2008 at 5:03 PM, Prologix [EMAIL PROTECTED] wrote: Hello Matt, It appears your Prologix GPIB-USB controller is in firmware update mode. Please follow these steps: 1. Disconnect USB cable and GPIB cable. If the controller is plugged onto an instrument, unplug it. 2. Connect USB cable. 3. Connect GPIB cable, or plug onto instrument. Let me know if you have more questions. That seems to fix things. Simply unplugging USB isn't enough -- I have to take it off the instruments as well. How do I keep from getting into that mode in the first place? I need this to work reliably without having to reconnect it several times a day. Matt ___ 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] Zeta Labs X76 Multiplier 7600 MHz Output Model 5856-01
On Mon, Apr 28, 2008 at 4:15 PM, Rick Karlquist [EMAIL PROTECTED] wrote: I worked for Zeta Labs many years ago. This multiplier undoubtedly has a step recovery diode that is being driven at a level of a good watt or two. In most cases there was a hefty transistor to make this power. You probably need +10 dBm or so to drive it, maybe as much as +20 dBm. Take the cover off and look at the input section and it should be apparent if there is any additional gain. You can always start at 0 dBm and work up, looking at the power out as you go along. The adjustment of these can be very tricky, so proceed with extreme caution. Rick, I just got the multiplier. It draws about 220mA at 15V, but won't produce any output. I've given it a wide range of input powers from very low up to about 20dBm. I took off the bottom cover, but it only exposes the back of a very complex circuit board. The only accessible parts are the trimmer caps which come through the PCB. Any suggestions? Thanks, Matt ___ 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] Zeta Labs X76 Multiplier 7600 MHz Output Model 5856-01
Just bought a Zeta Labs X76 Multiplier 7600 MHz Output Model 5856-01 on ebay. Anybody have any info on these? What kind of drive should I give it? Thanks, Matt ___ 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] Zeta Labs X76 Multiplier 7600 MHz Output Model 5856-01
Thanks Rick. My main reason for buying this is to be able to better measure the phase noise of my 100 MHz oscillator. I figured this would give a truer measure than a brick since there is no PLL involved. But then I thought there might be too much filtering going on. If the filters are at least several MHz wide, then it should be fine, but if there is a 100 MHz crystal filter in there, then it won't really give me a true measure. What do you think? Thanks, Matt On Mon, Apr 28, 2008 at 4:15 PM, Rick Karlquist [EMAIL PROTECTED] wrote: I worked for Zeta Labs many years ago. This multiplier undoubtedly has a step recovery diode that is being driven at a level of a good watt or two. In most cases there was a hefty transistor to make this power. You probably need +10 dBm or so to drive it, maybe as much as +20 dBm. Take the cover off and look at the input section and it should be apparent if there is any additional gain. You can always start at 0 dBm and work up, looking at the power out as you go along. The adjustment of these can be very tricky, so proceed with extreme caution. Especially the SRD assembly. There were rows and rows of technicians with sweepers who tuned these up. The sweepers would sweep typically 80 to 120 MHz. Some of the techs liked to listen to the radio as they worked, and since this frequency range encompased the FM band, the radio would make a woodpecker like sound all day long. The Zeta multipliers were fairly similar to the multiplier in the well known brick frequency sources (California Microwave, etc). Many people worked at both companies at various times. Rick Karlquist N6RK Matt Ettus wrote: Just bought a Zeta Labs X76 Multiplier 7600 MHz Output Model 5856-01 on ebay. Anybody have any info on these? What kind of drive should I give it? Thanks, Matt ___ 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] Racal-Dana 1992 switches
On Mon, Mar 10, 2008 at 8:47 AM, Dan Rae [EMAIL PROTECTED] wrote: David McGaw wrote: Does anyone know of a source of push-button switches for the Racal-Dana 1992? I have one that over half are bad. No luck from Racal-Dana or their service house. The original makers of that switch (Omron?) stopped making them years ago. I wonder why? The last time I did this I found a switch at Jameco that was a near exact replacement. The only difference was that the button was a little too loose a fit and needed a dab of epoxy inside to hold it firmly in place. These have been working in mine now for at least five years. The type I used was KIE22 (29 cents each in 100s), however the ones I got then with a cross section shape blue plunger do not look exactly the same as the ones pictured in the current on line catalog. Some further research is indicated obviously... Once they start to go they will all need to be replaced, I'm afraid. I bought the ones in the catalog, but they don't fit. The footprint is bigger, for one thing. Matt ___ 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] Racal counters
Since a bunch of the switches on my 1992 are bad, I was going to buy another to use for donor switches. However, I would also consider getting a 1990, 1995, or 1996 if those had more features. Anybody know the real differences from the 1992 to those other models? Thanks, Matt ___ 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] Racal-Dana 1992 switches
On Tue, Mar 11, 2008 at 1:05 PM, Dan Rae [EMAIL PROTECTED] wrote: [EMAIL PROTECTED] wrote: Are these switches the same as the ones in the 1996? Mine works perfectly now, but if the switches are a ticking time bomb, I'm going to move it to a area with better temperature control, and start looking for a donor unit just in case. They both used the same switches. However, not all batches of these seem to have suffered the problem. If any on a unit go they may well all die. Also it is possible that they may have been replaced at some time in the past, I knew a technician at the service dept here in California who did a lot of them way back, when they were still supported... It is hard to be more specific... From examination of the dead ones I remember it was a rubber insert that died. They start to feel a bit less springy than usual, then die. My 29 cent Jameco switches have worked for me for at least five years now. I don't think you would want to have paid racal's prices for them anyway :^) You guys are bad luck... My switches were all fine until you started talking about them dying... I desoldered one of them and it appears to be marked TOKO 30. I didn't know TOKO made switches, and none are listed on their web page. Would Racal still have them? Matt ___ 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] 100 MHz VCTCXO
I am trying to find a 100 MHz VCTCXO. The term VCTCXO doesn't seem to be universal, so what I mean is a crystal oscillator which is voltage tunable, but which without tuning is within about 10 or 20 ppm. Rakon has parts on their website which fit the bill, but they don't seem to actually make them. Does anyone know of a vendor which does? I know OCXOs would also work, but they would be too big and overpriced for this application. Thanks, Matt ___ 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] M1 OT scope tools
Anybody ever used M1 Oscilloscope Tools from Amherst Systems? http://www.amherst-systems.com/ It was pointed out to me today and it looks quite impressive. Is it worth it? Thanks, Matt ___ 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] gps timing antennas
Is there really anything in particular which is different about the antenna requirements of timing receivers as compared to ordinary high-quality receivers? The timing antennas seem to be in pointy radomes, so that tells me they are probably quad-helixes rather than patch antennas. How is that advantageous for timing in particular? Thanks, Matt ___ 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] GPS Locked and Unlocked Performance Comparison
On Feb 13, 2008 1:03 AM, Tom Van Baak [EMAIL PROTECTED] wrote: To prevent, or at least detect, this effect I allow my 10 MHz house reference to drift off-frequency by quite a bit (last month it was 1.7e-12 off). That way there are no on-time or on-frequency sources near the test setup. Tom, I think you might be the only person in the world who would consider 1.7 parts per trillion to be quite a bit off :) Matt ___ 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] Oscilloquartz 4533
Are these any good? http://www.oscilloquartz.com/index.php?pageid=37 Thanks, Matt ___ 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] Oscilloquartz 4533
On Feb 11, 2008 2:19 PM, Bruce Griffiths [EMAIL PROTECTED] wrote: Matt Ettus wrote: Are these any good? http://www.oscilloquartz.com/index.php?pageid=37 Thanks, Matt Matt The OCXO frequency holdover performance at 1E-10/day is respectable. The GPS receiver performance isnt stellar but still respectable. The non GPS version is perhaps less useful, although the internal OCXO will be. Thanks. I got one of these with GPS+OCXO off of ebay today. The seller had 2 for $399, but I did the make an offer thing at $235 and they accepted. I like the fact that it is small and takes a single power supply. Matt ___ 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] HP5342A GPIB programming
So, after a couple of hours messing with it, I finally got the counter
to tell me a frequency over GPIB. The magic incantations, in Python
are:
c.write('AUSR3LCT2ST2')
freq = c.read(20)
Once I got that working, I set it up to print out the frequency at 1
second intervals. That worked for 5 minutes, and now the GPIB
interface is essentially dead. The counter appears to hear and act on
commands, but some acknowledge pin must have died because everything
times out now. I think the GPIB is dead.
So, given that, anybody have any suggestions on a replacement? I just
need something that counts to a few hundred MHz, has GPIB, is
reliable, preferably small, and preferably doesn't have a loud fan?
Also, anyone interested in a 5342A which works fine other than the
GPIB interface?
Matt
On Jan 30, 2008 6:05 PM, John Miles [EMAIL PROTECTED] wrote:
Hmm, no, according to the 5342A manual, it uses CR+LF termination, so the
normal query.exe utility should work. It must be a triggering issue.
Try the command
query 2 AUSR4T2ST1 500
AU = auto frequency mode select (as opposed to M=manual)
SR4 = 10 Hz resolution
T2 = fast sample (no delay)
ST1 = output only when addressed
That's similar to Example 2 on page 3-25 of the manual, which doesn't rely
on the 'trg 702' statement in the first example. Either T0 or T2 mode (page
3-23) should work with query.exe; T1 may not.
Also try it with ST1 versus ST2 in the last three characters of the command,
to see if that makes a difference.
-- john, KE5FX
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Behalf Of John Miles
Sent: Wednesday, January 30, 2008 5:38 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] HP5342A GPIB programming
Sounds like a handshaking issue. It may not be related, but you
might take
a look at the 5345a.cpp example. The 5345A is kind of nonstandard in that
it terminates responses with CR (ASCII 13) rather than CR/LF
and/or EOI. I
have to set the EOS character to 13 in 5345a.cpp to receive any data from
it.
-- john, KE5FX
-Original Message-
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]
Behalf Of Matt Ettus
Sent: Wednesday, January 30, 2008 5:25 PM
To: Discussion of precise time and frequency measurement
Subject: [time-nuts] HP5342A GPIB programming
I have an HP5342A with GPIB, and am having trouble getting a reading
out of the GPIB interface. It seems to work ok, and when I send it
commands with talk.exe from the KE5FX GPIB tools, it responds to the
command. But any time I query it, it just sits there and times out,
although the front panel indicates something is happening. In the
manual, it talks about sending an HP BASIC command to trigger a
measurement, but I don't know how to do that with the command line
tools.
Any ideas?
Thanks,
Matt
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Re: [time-nuts] Spec An for phase noise measurements
On Jan 21, 2008 11:44 AM, John Miles [EMAIL PROTECTED] wrote: I am considering getting a new spectrum analyzer so I can make better phase noise measurements than with my 8596E. I've looked at the 8566B and the 8562 and 8563 since I need coverage to at least 6 GHz. The 8566 is huge and ancient, though, so I think I'm leaning away from that one. Anybody have other suggestions? Some of the Advantest units seem to be reasonably priced on ebay, but it is hard to figure out what their phase noise performance is. After working with a quadrature PLL/LNA, I feel very strongly that anyone who's serious about PN measurement should go this route. I wasted a lot of time myself, sitting around wishing I could afford a quieter spectrum analyzer. It's simply the wrong question to ask. It's true that the HP 8590s are among the noisiest spectrum analyzers out there, but the difference between the phase-noise floors of an 8596E and an 8560E is only about 20-25 dB. The difference in cost is several thousand dollars. If you invest in a nice 8662A instead -- or even an 8640B! -- you can use your *existing* 8596E to make measurements 30-40 dB below what even the 8560E series can do. John, I decided to get a new spectrum analyzer rather than an 11729 at this time. I bought an Advantest R3267 to replace the HP 8596E. It seems to have phase noise performance in the same neighborhood as the 8560-series, for about half the price. In case I ever need anything better, I can get an 11729 and use it with this analyzer, since it goes down to 100 Hz, unlike the 8596 which only went to 9kHz. I am seeing the following performance when measuring the built in 30 MHz reference: 100 Hz -81dBc 1 kHz-108 to -110 10 kHz -117 100 kHz -125 1 MHz-131 All of those are 3-8dB better than the spec, except for at 1 MHz where the spec is -135. The measurements do jump around a bit. I would really love to have PN.exe drive the analyzer so I can do real phase noise plots. I have an electronic copy of the manual, which has all the GPIB info, but the last time I dove into the PN code (in an aborted attempt to port it to Linux), I had a very hard time grokking the code, plus I don't have a Windows development environment. Is there any way we can work together on getting this analyzer supported? Several other Advantest machines are compatible with it, so any work would cover multiple models. Thanks, Matt ___ 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] Spec An for phase noise measurements
I am seeing the following performance when measuring the built in 30 MHz reference: 100 Hz -81dBc 1 kHz-108 to -110 10 kHz -117 100 kHz -125 1 MHz-131 All of those are 3-8dB better than the spec, except for at 1 MHz where the spec is -135. The measurements do jump around a bit. If I change to Digital mode for 100 Hz RBW, and turn on averaging, I get much better results from the analyzer -- 100 Hz-100dBc 1 kHz -110 10kHz -120 100kHz-129 1M-135 This, of course, makes me question all the measurements Matt ___ 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] Spec An for phase noise measurements
Sure, send me the GPIB .PDF, either via Didier's site, ftp.ko4bb.com, user manuals, password manuals) or via my GMail account at [EMAIL PROTECTED] It looks like a great spectrum analyzer considering the prices they seem to fetch on eBay. Should be a nice upgrade from the 8596E, all right. Great! I sent the manuals to your email account. Loks like everything GPIB is in chapter 5 of volume 1. The only requirement is that I need to be able to count on you to test the code *carefully*. This can be a trying process, because PN.EXE has to carry out a lot of interaction with the spectrum analyzer, and it's tough to write code for one that isn't sitting on my workbench. I can do that. The ideal scenario is one where I have a remote-desktop account on a WinXP box at your end, I can look into doing that, but I've never tried it before. I'm a Linux guy, so point me in the direction you need... with an NI or Prologix board connected to the R3267. That takes you out of my edit-compile-test loop. :) That's not vital, but it really helps speed things up. I've got it hooked up on an NI GPIB-USB-B adapter. Matt ___ 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] Spec An for phase noise measurements
On Jan 23, 2008 4:26 PM, John Miles [EMAIL PROTECTED] wrote: Are you using a noise marker that yields dBc/Hz values? The FFT window function has its own required noise-response correction value, so if you're just looking at a marker and doing the log10(RBW) subtraction yourself, that could account for the difference. Also, if there is a noise marker, check to see if it reads dBc/Hz or dBm/Hz. Most of them read dBm/Hz values, which are obviously only equal to conventional dBc/Hz values if you're measuring a 0-dBm carrier. I used the analyzer's phase noise function. It won't make a plot, but will do measurements at a few spot offsets. It's not entirely clear how it is calculating these, though. Matt ___ 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] Spec An for phase noise measurements
I am considering getting a new spectrum analyzer so I can make better phase noise measurements than with my 8596E. I've looked at the 8566B and the 8562 and 8563 since I need coverage to at least 6 GHz. The 8566 is huge and ancient, though, so I think I'm leaning away from that one. Anybody have other suggestions? Some of the Advantest units seem to be reasonably priced on ebay, but it is hard to figure out what their phase noise performance is. Also, what is the difference between the A, B, and E models on the 8560 series? The A models are much cheaper on ebay. Thanks, Matt ___ 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] Spec An for phase noise measurements
On Jan 21, 2008 11:44 AM, John Miles [EMAIL PROTECTED] wrote: After working with a quadrature PLL/LNA, I feel very strongly that anyone who's serious about PN measurement should go this route. I wasted a lot of time myself, sitting around wishing I could afford a quieter spectrum analyzer. It's simply the wrong question to ask. It's true that the HP 8590s are among the noisiest spectrum analyzers out there, but the difference between the phase-noise floors of an 8596E and an 8560E is only about 20-25 dB. The difference in cost is several thousand dollars. If you invest in a nice 8662A instead -- or even an 8640B! -- you can use your *existing* 8596E to make measurements 30-40 dB below what even the 8560E series can do. This is a seriously-nice thing to be able to do at home. You can use a quadrature PLL to do things like compare different crystal-oscillator circuits and look at DDS phase-noise floors... and lots of other things you would never be able to do with a spectrum analyzer alone. I'll see if the list will let me attach a small .GIF showing the difference. The 11729C's noise floor is about 6-10 dB below the green trace, which is a comparison of a couple of decent-quality 100 MHz OCXOs. Note how much higher the direct measurement floors of your current spectrum analyzer and an 8560E are. For $25 in parts, you could make the measurement in the green trace with your 8596E! Spend the extra money on signal generators, and/or collecting VCXO references at various frequencies. John, I'm a little confused as to what you are suggesting. An 8662A is about $1500, and the 11729C is about $3k. What would I get for $25? I don't know exactly what is involved with the 11729 and how it makes measurements. If I just connected a quadrature PLL and LNA, I would still need a very clean VCO at the same frequency, right? Thanks, Matt ___ 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] Spec An for phase noise measurements
On Jan 21, 2008 12:09 PM, John Miles [EMAIL PROTECTED] wrote: Still, you should keep what you already have, and add a quadrature PLL and LNA to it. As a more-concrete answer to your question, since you mentioned a need for coverage into the 6-GHz region, an 11729B/C and 8662A would actually be a good choice. Together they'll still be much cheaper than the 8561E I'd recommend otherwise. Figure $2500 at most for the 8662A and $1200 at most for the 11729B/C. That's where you lose me -- the 8662A only goes to 1.28 GHz, right? Do you use multipliers? Matt ___ 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] Spec An for phase noise measurements
On Jan 21, 2008 12:41 PM, John Miles [EMAIL PROTECTED] wrote: John, I'm a little confused as to what you are suggesting. An 8662A is about $1500, and the 11729C is about $3k. What would I get for $25? The parts needed to implement Wenzel's app note: http://www.wenzel.com/documents/measuringphasenoise.htm I don't know exactly what is involved with the 11729 and how it makes measurements. Take an hour and look through this HP app note (large file, but only about 50 pages): http://www.thegleam.com/ke5fx/gpib/5952-8286E.pdf It is not all that specific to the 11729B/C despite making frequent references to it. Makes sense now. One problem -- the 8596E only goes down to 9kHz, at least according to the specs. Matt ___ 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] Locking 100 MHz to 10 MHz
I am designing a system where I lock a 100 MHz VCXO to a 10 MHz reference using an AD9510 clock PLL chip. I have two questions to which I don't know the answer: - First, given the specs of both oscillators, I know how to choose the right loop bandwidth. The problem is that I have no idea what kind of 10 MHz oscillators people are going to connect. The 100 MHz osc typical specs for phase noise are: 10Hz -65dBc 100Hz-68dBc 1k -98 10k-140 100k to 100MHz -145 I was thinking of just going with a 1kHz bandwidth, for lack of any better ideas. - Second, for when there is no 10 MHz reference connected, the system needs to be brought to a reasonable frequency. The PLL charge pump outputs are tri-stated. On the end of the loop filter, right before the control voltage input to the VCXO, I have a resistor divider to center the voltage between 3.3V and ground. I use 100K resistors in the hope that they will not affect things when the loop is active, but I can't really tell, since all the phase noises involved are well below the ability of my equipment to measure. Is this a safe technique, or am I messing up the performance while the loop is locked? Thanks, Matt ___ 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] Super Regulator links
He has ultra high performance rectifier bridges. Sounds like snake oil to me. Matt On Dec 13, 2007 5:57 PM, Bruce Griffiths [EMAIL PROTECTED] wrote: Revised Super regulator link is: http://www.sjostromaudio.com/_unsql/hifi/ However this may change as the website is in process of moving. It works at the moment. Bruce ___ 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] Super Regulator links
On Dec 13, 2007 6:15 PM, Bruce Griffiths [EMAIL PROTECTED] wrote: Matt Ettus wrote: He has ultra high performance rectifier bridges. Sounds like snake oil to me. Matt Try looking at the circuit before commenting. I did. Different culture express themselves in slightly different ways, its best to study the actual circuit and think about what the designer may mean by the term. You will find that he actually uses fast recovery diodes with snubbers to reduce RFI. Can you explain to me the use of fast recovery diodes if you are going to put capacitors across them? You also have to bear in mind the market into which he is selling these devices, they expect some hype of this sort. The market he is selling into expects snake oil. Matt ___ 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] An Excellent Tutorial on Precision Clocks
What I've seen is that field solvers, which don't rely on closed-form solutions seem to be the state of the art. Matt On 3/14/07, Dr Bruce Griffiths [EMAIL PROTECTED] wrote: Matt Ettus wrote: I was just investigating this very issue. It seems that every program you use to compute these impedances comes up with different answers, sometimes wildly different. Anyone have a free program they trust with this sort of thing? Matt On 3/14/07, Dr Bruce Griffiths [EMAIL PROTECTED] wrote: Tom Clark, K3IO wrote: I just stumbled on an excellent tutorial on low-noise clocks -- National Semiconductors free downloadable [1]Clock Conditioner Owner's Manual. This 88 page document is a 3.7 MB PDF. 73 de Tom, K3IO References 1. http://www.national.com/appinfo/interface/files/clk_conditioner_owners_manual.pdf ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts Tom Not bad except they give inaccurate formulae for stripline and microstripline characteristic impedance. Will these inaccurate formulae ever go away? They've been around since the 1970's. When with the trace widths and board thickness then in use the accuracy wasn't too bad. However they are not very useful for modern PCB design. 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 Matt The formulae given in Johnson and Graham's High speed Digital Design are reliable. However there's no substitute for measurement to check your calculations, 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
Re: [time-nuts] An Excellent Tutorial on Precision Clocks
I was just investigating this very issue. It seems that every program you use to compute these impedances comes up with different answers, sometimes wildly different. Anyone have a free program they trust with this sort of thing? Matt On 3/14/07, Dr Bruce Griffiths [EMAIL PROTECTED] wrote: Tom Clark, K3IO wrote: I just stumbled on an excellent tutorial on low-noise clocks -- National Semiconductors free downloadable [1]Clock Conditioner Owner's Manual. This 88 page document is a 3.7 MB PDF. 73 de Tom, K3IO References 1. http://www.national.com/appinfo/interface/files/clk_conditioner_owners_manual.pdf ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts Tom Not bad except they give inaccurate formulae for stripline and microstripline characteristic impedance. Will these inaccurate formulae ever go away? They've been around since the 1970's. When with the trace widths and board thickness then in use the accuracy wasn't too bad. However they are not very useful for modern PCB design. 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
Re: [time-nuts] Carrier phase tracking
On 2/20/07, Peter Vince [EMAIL PROTECTED] wrote: I don't wish to offend, but that is totally wrong. Even if every satellite were on the exact same frequency, with the exact same doppler, and the exact same direction, you would still have no problem separating the carriers of the multiple satellites. The reason is that the satellites do not transmit carrier. Here is how: Everybody here understands how the PN codes are tracked by despreading. The despreading operation is multiplication, and when you multiply the PN code by the original signal you get a carrier, only from that one satellite. Do you? Or do you just get the modulation? Yes, you get the 50 bps modulation. But since you can demod the bits, you can then multiply the bits into the signal, then you get the carrier. In practice, you don't usually get to a time sampled sequence of the carrier. You typically track it in a pll whose output is frequency and phase. Matt ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Carrier phase tracking
On 2/19/07, Poul-Henning Kamp [EMAIL PROTECTED] wrote: Does it rely on the different Doppler-shifts making them distinguishable? It would have to, if they were not on different frequencies, they would sum to a single sinewave and you couldn't tell them apart (unless you have a direction sensitive antenna). I don't wish to offend, but that is totally wrong. Even if every satellite were on the exact same frequency, with the exact same doppler, and the exact same direction, you would still have no problem separating the carriers of the multiple satellites. The reason is that the satellites do not transmit carrier. Here is how: Everybody here understands how the PN codes are tracked by despreading. The despreading operation is multiplication, and when you multiply the PN code by the original signal you get a carrier, only from that one satellite. Despread with a different PN code, and you get a different carrier. Thus, while the frequencies may all be the same, they are in separate signals, one out of each correlator. Matt ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] TAPR Clockblock and USRP (GnuRadio) anyone ?
On 1/13/07, Poul-Henning Kamp [EMAIL PROTECTED] wrote: In message [EMAIL PROTECTED], [EMAIL PROTECTED] writes: Actually the USRP v4 seems to have a VCXO already: http://gnuradio.org/svn/usrp-hw/trunk/USRP_REV_4_2/clock.pdf Actually, it isn't. Its a plain crystal oscillator. Selected for very low jitter, but it does have up to 50 ppm drift over temperature. Matt ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] PLL Phase Noise vs. Divider Jitter
I'm aware that they use mixers at higher frequencies, but what are one's alternatives at low frequencies such as a 10MHz reference? The real answer is not to divide down your reference. This takes modern PLL chips capable of using a high reference frequency. If you need fine tuning capability, then you'll have to use a fractional-N PLL. Analog Devices has a program called ADISimPLL which allows you to play with all these factors using real parts. Matt ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] PLL Phase Noise vs. Divider Jitter
In the previous thread, HP 58540A Phase Noise Improvements, Matt Ettus noted the following: The jitter that is added by a divider would most probably pose a greater limit to the phase noise of the PLL than that of the specific OCXO used. This sounds a little strange. Most of the jitter will be filtered out by the PLL loop filter. Since we discuss OCXO we are discussing fairly moderate frequencies (5-20 MHz) and acheiving low jitter dividers should not be a problem. Low jitter dividers still have phase noise floors higher than what he's looking for. Check out the figure of merit in modern PLL chips. Matt ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] M12T and M12M
Can somebody tell me the master clock frequency of the M12T and M12M GPS receivers? Thanks, Matt ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] M12T and M12M
Is there logic (that I'm missing) to what seems like such an odd frequency? Matt On 6/14/06, Randy Warner [EMAIL PROTECTED] wrote: Tom, You're close. The M12 series actually has a 16.367 MHz crystal (TCXO in the M12M). What enables the M12 to get down to +/-12 ns is that it can place the 1PPS on both the rising and falling edges of the clock. Randy -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Tom Van Baak Sent: Wednesday, June 14, 2006 2:39 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] M12T and M12M Can somebody tell me the master clock frequency of the M12T and M12M GPS receivers? Thanks, Matt The old Oncore VP used a 9.54 MHz oscillator and had sawtooth error of about 104 ns (+/- 52 ns). The M12 has jitter closer to 25 ns (+/- 12 ns) which would imply a clock frequency of approximately 40 MHz. See also: http://www.leapsecond.com/pages/m12/sawtooth.htm /tvb ___ 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] How Rubidiums make their frequency
Since we can now make DDS's with arbitrary frequency resolution, could you make an Rb oscillator without the magnetic field adjustment? Wouldn't that reduce a source of error in frequency? Then we'd be left with the ideal resonance frequency, right? Are there any other influences on the resonance frequency? I assume temperature and density don't matter. Matt On 4/19/06, Tom Clark, K3IO (ex W3IWI) [EMAIL PROTECTED] wrote: Christopher Hoover asked: one issue remains: i have to crank the magnetic field setting almost to its high limit (9.91/10.00) to get 5 MHz out; lower settings give a frequency that is too low. i presume this is unusual. i have a rudimentary understanding of the rubidium oscillator physics, but i do not understand what would cause this. can i buy a clue? I don't know the Tracor, but I imagine it is like most of the other Rubidiums in it's innards. Inside the physics package of a Rb, a cell with some Rubidium is heated to (that's why Rb's run not!) enough so that it is turned into a gas. Both light and microwaves illuminate the cell. If no magnetic field is present on the cell, the Rb gas has a hyperfine resonance (the difference in frequency between two infrared transitions of the Rb gas) at 6.8346826128 Mhz. When a magnetic field is imposed, the energy difference between the two hyperfine states changes. In the RF part of the signal path (here, the block digram of a typical Rb standard helps. See Page 3 of [1]this Symmetricom White Paper .) Let's start with some convenient oscillator at, let's say 10 MHz. Multiply it up to 60 MHz and then hit a Step Recovery Diode to get the 114th harmonic at 6840 MHz. Then difference between the 6834.. and 6840 MHz is 5.31738+ MHz. In the standard Rb configuration, we apply a magnetic C-field to bring the difference frequency upwards by 4.89 kHz to 5.3125 MHz which happens to be 5MHz + 5/16MHz. Back in the early days, we didn't have nice programmable DDS chips, but simple dividers/multipliers could make the 5/16 MHz adder. So what you are doing by tweaking the magnetic field to shift the RF resonance of the Rb cell so that it matches the arithmetic quirk that the 6834 MHz is almost contains the neat 5/16 MHz in the tail-end digits. Hope that helped -- 73, Tom References 1. http://www.symmttm.com/pdf/Precision_Frequency_References/wp_mmrfs.pdf ___ 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] Short-Term Stability
Let me know if you would like to get more detailed info on how we implemented the GPSDO and DDS, and the caveats we ran into etc. I'd like to hear more about this. Thanks, Matt ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Accuracy of a sound card
On 8/22/05, Tom Van Baak [EMAIL PROTECTED] wrote: I measured the phase, frequency and Allan deviation of the sound card on my cheap PC. You'll enjoy the results: http://www.leapsecond.com/pages/sound-1pps/ If any of you with a high-end sound card want to repeat the experiment let me know. All common soundcards have an oscillator that is either a multiple of 48 kHz or of 44.1 kHz. They fake it for other sample rates. It would be interesting to see if the same experiment with a 48 kHz sample rate produced different results. Matt ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
[time-nuts] Code for phase noise and allan variance
Does anyone have code which will take an amplitude vs. time input stream and output phase noise and/or allan variance? Thanks, Matt P.S. I was forwarded a message from the list about the USRP. The USRP does have an input for an external clock source, so feel free to feed it from your Hydrogen Maser or whatever else you have laying around :) The reference needs to be at 64 MHz or lower. You ADC sample rate can be 1/4*fref, 1/2*fref, fref, or 2*fref, as long as the final rate is = 64 MHz. The DAC sample rate will always be 2*fref. Matt ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
Re: [time-nuts] Code for phase noise and allan variance
On 6/27/05, Poul-Henning Kamp [EMAIL PROTECTED] wrote: In message [EMAIL PROTECTED], Matt Ettus writes: Does anyone have code which will take an amplitude vs. time input stream and output phase noise and/or allan variance? http://phk.freebsd.dk/misc/Allan.tgz will do allan, modified allan and FFT. Thanks! I tried to compile on Linux, got this: [EMAIL PROTECTED] Allan]$ make Makefile:9: *** missing separator. Stop. I removed the last line in the Make file and got this: [EMAIL PROTECTED] Allan]$ make cc -g -Wall -staticallan.c -o allan allan.c:19:27: floatingpoint.h: No such file or directory allan.c: In function `main': allan.c:722: warning: implicit declaration of function `fpsetmask' allan.c:722: error: `FP_X_UFL' undeclared (first use in this function) allan.c:722: error: (Each undeclared identifier is reported only once allan.c:722: error: for each function it appears in.) make: *** [allan] Error 1 Looks like I'm missing floatingpoint.h. A BSD thing? Matt ___ time-nuts mailing list time-nuts@febo.com https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
