Re: [time-nuts] Rb as source for ADEV?
On 09/02/14 05:48, Hal Murray wrote: b...@evoria.net said: Would I learn anything useful by hooking my Rb standard up to my 5335A and comparing that to the OCXO? What kind of time-nut question is that? :) Try it and see. Maybe you will find something interesting where you/we didn't expect it. If you assume the Rb is stable, you should be able to watch the long term drift of the OCXO. You can also see temperature variations. How many low digits can you get out of the 5335A? Has 1 ns resolution. Can do averaging on it's own but I rather use TimeLab or something. Do you have an GPSDO to add to the mix? That would let you calibrate the Rb. And you can measure the long-term drift of your rubidium with the same setup. 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.
Re: [time-nuts] Rb as source for ADEV?
Hi Hal, I'm thinking about doing it, but I'm still doing extended tests of my GPSDO with the 5334B. So in order to get access to the 5335A, I'll have to write a server for my Prologix GPIB Ethernet adapter. I've got a lot of time nuts projects stacked up, and it looks like the GPIB server is going to be key to all of them. Bob - AE6RV From: Hal Murray hmur...@megapathdsl.net To: Bob Stewart b...@evoria.net; Discussion of precise time and frequency measurement time-nuts@febo.com Cc: hmur...@megapathdsl.net Sent: Saturday, February 8, 2014 10:48 PM Subject: Re: [time-nuts] Rb as source for ADEV? b...@evoria.net said: Would I learn anything useful by hooking my Rb standard up to my 5335A and comparing that to the OCXO? What kind of time-nut question is that? :) Try it and see. Maybe you will find something interesting where you/we didn't expect it. If you assume the Rb is stable, you should be able to watch the long term drift of the OCXO. How many low digits can you get out of the 5335A? Do you have an GPSDO to add to the mix? That would let you calibrate the Rb. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Rb as source for ADEV?
Bob, If you want a C++ class to talk to the Prologix Ethernet, I have one. (I don't have a USB version, but that would just be a matter of implementing a simple subclass to do the communication with the device.) I also have code that uses the above and talk to a 5335A and to a 5370A, both of which like to sulk if you don't do things in the right order. It's written for Windows and should compile in the _free_ Visual Studio Express 2012 (it used to, but the last time I built it was with the full version). Porting to Linux/Mac/iOS would be easy enough... maybe I'll do iOS for fun, if Xcode doesn't sulk and stays alive long enough that is; the only thing Xcode does fast for me is crash! Licensing for all but the findAdapters method will be LGPL once I put headers in. findAdapters() is derived from John Miles's GPIB library and subject to its licensing. Orin, KJ7HQ On Sun, Feb 9, 2014 at 7:36 AM, Bob Stewart b...@evoria.net wrote: Hi Hal, I'm thinking about doing it, but I'm still doing extended tests of my GPSDO with the 5334B. So in order to get access to the 5335A, I'll have to write a server for my Prologix GPIB Ethernet adapter. I've got a lot of time nuts projects stacked up, and it looks like the GPIB server is going to be key to all of them. Bob - AE6RV From: Hal Murray hmur...@megapathdsl.net To: Bob Stewart b...@evoria.net; Discussion of precise time and frequency measurement time-nuts@febo.com Cc: hmur...@megapathdsl.net Sent: Saturday, February 8, 2014 10:48 PM Subject: Re: [time-nuts] Rb as source for ADEV? b...@evoria.net said: Would I learn anything useful by hooking my Rb standard up to my 5335A and comparing that to the OCXO? What kind of time-nut question is that? :) Try it and see. Maybe you will find something interesting where you/we didn't expect it. If you assume the Rb is stable, you should be able to watch the long term drift of the OCXO. How many low digits can you get out of the 5335A? Do you have an GPSDO to add to the mix? That would let you calibrate the Rb. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Rb as source for ADEV?
Hi If both / all of the counters are collecting 1 second data, the GPIB stuff isn’t going to be to bad … There’s always an If. You need to run the counters so they do it all automatically (arm etc). That’s the way it’s normally done It should not be to big a constraint. The rest of it turns into a poll this poll that loop. When one of the counters has data you grab it and shove it into a file someplace. The counters buffer the data, so they only get bothered if the poll / read process gets to a significant fraction of a second. They started out doing HPIB / GPIB with some *very* slow hardware. The 5335 and 5334 date to that era. They have been fully debugged with gear that waits a while to grab data from them. If you are running a lot faster then yes… you can get into issues. Bob On Feb 9, 2014, at 4:28 PM, Bob Stewart b...@evoria.net wrote: Hi Orin, No, it's not a matter of just talking to the device. I can to that. The problem happens when you want more than one program/process to access the GPIB bus at the same time; e.g. running two different tests. For that you have to have a server process which manages the interface and relays packets to the clients. Prologix hadn't written one when they commented here last summer. Bob From: Orin Eman orin.e...@gmail.com To: Bob Stewart b...@evoria.net; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, February 9, 2014 12:55 PM Subject: Re: [time-nuts] Rb as source for ADEV? Bob, If you want a C++ class to talk to the Prologix Ethernet, I have one. (I don't have a USB version, but that would just be a matter of implementing a simple subclass to do the communication with the device.) I also have code that uses the above and talk to a 5335A and to a 5370A, both of which like to sulk if you don't do things in the right order. It's written for Windows and should compile in the _free_ Visual Studio Express 2012 (it used to, but the last time I built it was with the full version). Porting to Linux/Mac/iOS would be easy enough... maybe I'll do iOS for fun, if Xcode doesn't sulk and stays alive long enough that is; the only thing Xcode does fast for me is crash! Licensing for all but the findAdapters method will be LGPL once I put headers in. findAdapters() is derived from John Miles's GPIB library and subject to its licensing. ___ 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] Rb as source for ADEV?
Somewhat like Bob (Stewart) I've spent my life in IT with a little background in Ham Radio. Now, infected with the Time Bug, I'm slogging through tf.nist.gov, wenzel, and leapsecond to try and level up. I'd like to ask Bob (Camp) if he has a readily available link for a suitably quite homebrew mixer, similar to the one whose parts list he was discussing? Thanks to Magnus for his links (later in this thread), to which I'd like to add the following for those on the list, like me, who are neophytes. Fundamentals of Time and Frequency: http://tf.nist.gov/general/pdf/1498.pdf Using a Time Interval Counter to Measure Frequency Stability: http://ipnpr.jpl.nasa.gov/progress_report/42-90/90S.PDF The later link, while a little dated, still does a good job of covering concepts. Thanks again, Jimmy... N5SPE On Feb 6, 2014, at 8:57 PM, Bob Stewart b...@evoria.net wrote: I think I see the problem. I was wondering about using the 1PPS output from my Rb in a test. Cobbling all that together would be a quick bit of work for you, but I spent my life in IT. I'm good with a soldering iron, but I readily admit my shortcomings at hardware tinkering. Bob From: Bob Camp li...@rtty.us To: Tom Van Baak t...@leapsecond.com; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, February 6, 2014 7:43 PM Subject: Re: [time-nuts] Rb as source for ADEV? Hi My intent was certainly not to stop anybody from doing anything with what they have. My concern is that this is a lot of work for modest return. A simple single mixer setup for $20 would dramatically change things…. $3 mini circuits double balanced mixer $3 op amps x 2 +/- 15 V supply you already have (hopefully). $5 for a piece of perf board $3 for 3 BNC connectors. $3 left over for resistors and capacitors. snip ___ 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] Rb as source for ADEV?
Hi I pretty much wire them up on a piece of perf board when I need them. I’ve never bothered to do a real pc board. The OP-27 and OP-37 op amps are getting a bit old / expensive. If I was going to do one, I’d probably do some digging on the op amps first. There may be new(er) parts that are cheaper. Like anything else, done one up there’s a lot more pain involved doing one than doing a batch. PC boards make things easier. ——— The real benefit comes from a couple things: 1) Mixing down to a lower frequency. The counter gives you 9 digits a second no matter what the ( 1Hz) input. Lower frequencies give you more digits. Any reasonably quiet mixer will do this for you. That includes the DBM’s with connectors on them. 2) Amplifying the beat note as much as you can ahead of the limiter. Slew rate matters. Any *quiet* audio amp will do this for you, provided it’s got the frequency response and is very quiet at the low end. 3) Limiting with a circuit that has good noise performance at low frequencies. The poor guy who did the counter could not just focus on the low end. We can. There’s lots of ways to do each of those things. You can easily improve any of the three “chunks” over the very simple circuit I outlined. You can easily get caught up in the optimization process and turn this into a very complex project. For one second ADEV at the 1.0 x 10^-12 level (1x10^-13 at 10, 1x10^-14 at 100, 1x10^-15 at 1000) a very simple circuit will do the job. — The other alternative is to get something brand new with warranty and support like a TimePod. Symmetricom will happily sell you one. They work amazingly well and there’s no muss no fuss comparing a pair of devices. They are just a bit over the $10 to $15 budget (like by three zeros). Accuracy wise it will crush my little circuit, and mine doesn’t come with a cool GUI that reports power levels and the like. Am I trying to sell you one of these - no of course not. The point is that there’s a massive step cost wise going to new gear. Even at ten cents on the dollar there’s still a massive step. (and yes in this case you *can* take that as a “anybody want to sell a TimePod for 10 cents on the dollar?” question, I’m in a shopping mood … contact off list of course). I’m not holding my berth for the inbox filling up with offers. Finding this kind of gear used in good condition at a good price is not easy. — One other approach would be group builds. There are a number of these going on off list and aimed at selling the result. Because of the off list nature of this, it’s often tough to know what people are doing and how well they are doing. They tend to turn into limited production run builds and then vanish. Short runs make it tough for newcomers to stock up on stuff. There simply isn’t enough need for these things to keep a steady supply readily available. That’s not at all unique to this area. A *lot* of hobby electronics (and mechanics and ..) has exactly the same issue. I could fill several pages with examples. — Long rambling reply to a simple question - sorry about that …. Bob On Feb 8, 2014, at 6:02 AM, Jimmy Burrell jimmydb...@gmail.com wrote: Somewhat like Bob (Stewart) I've spent my life in IT with a little background in Ham Radio. Now, infected with the Time Bug, I'm slogging through tf.nist.gov, wenzel, and leapsecond to try and level up. I'd like to ask Bob (Camp) if he has a readily available link for a suitably quite homebrew mixer, similar to the one whose parts list he was discussing? Thanks to Magnus for his links (later in this thread), to which I'd like to add the following for those on the list, like me, who are neophytes. Fundamentals of Time and Frequency: http://tf.nist.gov/general/pdf/1498.pdf Using a Time Interval Counter to Measure Frequency Stability: http://ipnpr.jpl.nasa.gov/progress_report/42-90/90S.PDF The later link, while a little dated, still does a good job of covering concepts. Thanks again, Jimmy... N5SPE On Feb 6, 2014, at 8:57 PM, Bob Stewart b...@evoria.net wrote: I think I see the problem. I was wondering about using the 1PPS output from my Rb in a test. Cobbling all that together would be a quick bit of work for you, but I spent my life in IT. I'm good with a soldering iron, but I readily admit my shortcomings at hardware tinkering. Bob From: Bob Camp li...@rtty.us To: Tom Van Baak t...@leapsecond.com; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, February 6, 2014 7:43 PM Subject: Re: [time-nuts] Rb as source for ADEV? Hi My intent was certainly not to stop anybody from doing anything with what they have. My concern is that this is a lot of work for modest return. A simple single mixer setup for $20 would dramatically change things…. $3 mini circuits double balanced mixer $3 op amps x 2
Re: [time-nuts] Rb as source for ADEV?
b...@evoria.net said: Would I learn anything useful by hooking my Rb standard up to my 5335A and comparing that to the OCXO? What kind of time-nut question is that? :) Try it and see. Maybe you will find something interesting where you/we didn't expect it. If you assume the Rb is stable, you should be able to watch the long term drift of the OCXO. How many low digits can you get out of the 5335A? Do you have an GPSDO to add to the mix? That would let you calibrate the Rb. -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Rb as source for ADEV?
Hi If you want one second ADEV (or something close to it) you need a beat note that’s above 1Hz. If one second is not of interest, then lower is fine. If you want to use a normal OCXO as the offset oscillator, you need to be inside it’s trim range (either high or low). That rules out anything much over 10 Hz at 10 MHz unless you have some unusual OCXO's. Most 10 MHz OCXO’s will tune a hertz or more off of 10 MHz. Digital Rb’s like the 5680 will make it a bit further if you pick which side you tune to. You are after another 3 or 4 digits ( ppb’s - ppt’s) . 10 Hz might (but won’t) get you another 6 digits. Any offset you get by tuning a good OCXO will do what you need to do. Yes there are other more complicated ways to do this. Yes they can get you to a lower floor. If you are looking at an Rb or most GPSDO’s, there’s no need for anything more complicated. 90% of it is audio and non-critical in terms of layout. If you did it on a real board and bought the parts in any sort of quantity, raw cost could be below $10 without the connectors. And before I get clobbered again, no I’m not trying to sell the boards. Bob On Feb 6, 2014, at 9:47 PM, Hal Murray hmur...@megapathdsl.net wrote: Bob Camp li...@rtty.us: Offset the local reference one hertz or so and let the 5334 do it’s thing. Any hints on how to get a good oscillator that's off by 1 Hz from 10 MHz? How did you pick 1 Hz? Is 10 Hz offset better? How about 0.1 Hz? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Rb as source for ADEV?
All my 10811 will do 20 Hz. Sent from Samsung tabletHal Murray hmur...@megapathdsl.net wrote: Bob Camp li...@rtty.us: Offset the local reference one hertz or so and let the 5334 do its thing. Any hints on how to get a good oscillator that's off by 1 Hz from 10 MHz? How did you pick 1 Hz? Is 10 Hz offset better? How about 0.1 Hz? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Rb as source for ADEV?
I'm getting a little more familiar with ADEV and OADEV now. With a little help from Tom, I've put together gnuplot scripts and his software to get a decent plot. But, as some time-nuts have pointed out, my measurements are of one part of my system being compared to another. Would I learn anything useful by hooking my Rb standard up to my 5335A and comparing that to the OCXO? How long should I let the Rb heat up before starting the test? I'm a bit uncertain about the result of comparing a stable clock of questionable accuracy to an accurate clock of questionable stability. Hopefully I said that right. thanks, Bob - AE6RV ___ 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] Rb as source for ADEV?
Hi Bob, Short-term measurements like that do a good job using a OCXO and TIC to reveal TIC and GPS resolution limits. It's a useful exercise, but it usually doesn't tell you anything about the OCXO itself. Long-term measurements like that do a superb job using GPS to measure the long-term stability and frequency drift rate of the OCXO (or Rb). This, because for intervals of days to weeks to months you can't beat GPS as an inexpensive ultimate time/frequency standard. And for those long intervals, the TIC resolution is usually more than enough. Just collect the raw phase data and raw DAC data. In a few weeks you'll be able to make some really nice plots. Also consider freezing the DAC for a week (unlocked) and compare that data with your locked data. You can then make plots that look like: http://leapsecond.com/pages/gpsdo/ On Rb -- since you're now a time nut, do not let the Rb warm up at all -- the data get you the first hour or first day will be just as interesting as the data you collect the next month. On ADEV -- I know the source code calls them adev and oadev, but you should just call it ADEV. No one uses the old back-to-back formula anymore; the overlapping formula is the default. And then plot using the all or many tau method I mentioned. /tvb - Original Message - From: Bob Stewart b...@evoria.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, February 06, 2014 2:23 PM Subject: [time-nuts] Rb as source for ADEV? I'm getting a little more familiar with ADEV and OADEV now. With a little help from Tom, I've put together gnuplot scripts and his software to get a decent plot. But, as some time-nuts have pointed out, my measurements are of one part of my system being compared to another. Would I learn anything useful by hooking my Rb standard up to my 5335A and comparing that to the OCXO? How long should I let the Rb heat up before starting the test? I'm a bit uncertain about the result of comparing a stable clock of questionable accuracy to an accurate clock of questionable stability. Hopefully I said that right. thanks, Bob - AE6RV ___ 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] Rb as source for ADEV?
Hi Your Rb should be good to about 10 ppt at 1 second. Thats 10 ps. Your OCXO might be good to 1 to 10 ppt at 1 second that’s 1 to 10 ps. Your 5334 has a measurement resolution of 2 ns single shot (which is what matters in this case), that’s 2000 ps. You would like to have a resolution 5X better than the thing you are trying to measure. Your counter gate time error in ppt scales directly as tau. It’s always 2 ns, but at 10s tau it’s going to be 200 ppt not 2,000 ppt. Your Rb ADEV likely scales as square root of tau. At 100 seconds it’s 1 ppt, which would be 100 ps. You still aren’t there yet. Who knows what the OCXO is doing, let’s say it’s = 10 ppt. Still not there. At 10,000 seconds the Rb might get to 0.1 ppt. That would be 1,000 ps. Your counter still isn’t there. Who knows what the OCXO is doing at 10,000 seconds. The counter might follow the OCXO. ——— Simple answer - doing this directly with a counter is not the best approach. Bob On Feb 6, 2014, at 5:23 PM, Bob Stewart b...@evoria.net wrote: I'm getting a little more familiar with ADEV and OADEV now. With a little help from Tom, I've put together gnuplot scripts and his software to get a decent plot. But, as some time-nuts have pointed out, my measurements are of one part of my system being compared to another. Would I learn anything useful by hooking my Rb standard up to my 5335A and comparing that to the OCXO? How long should I let the Rb heat up before starting the test? I'm a bit uncertain about the result of comparing a stable clock of questionable accuracy to an accurate clock of questionable stability. Hopefully I said that right. thanks, Bob - AE6RV ___ 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] Rb as source for ADEV?
Simple answer - doing this directly with a counter is not the best approach. Most of us work with what we have. I think it's pretty cool what Bob is doing with a 5335A. Someday he may buy or build something better. Your best may not be his best, or my best. What is best at one tau is not at another. Time-nuts has never been about being best (otherwise we all loose to USNO); it's about learning and exploring this interesting field of time frequency with what we have at home, whether it's the ADEV of 60 Hz or ADEV of a 5335A/GPSDO, etc. /tvb ___ 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] Rb as source for ADEV?
On 2014-02-06 15:13, Tom Van Baak wrote: On ADEV -- I know the source code calls them adev and oadev, but you should just call it ADEV. No one uses the old back-to-back formula anymore; the overlapping formula is the default. And then plot using the all or many tau method I mentioned. /tvb I never knew about these different versions of ADEV. Can you point me to any reference? Rick ___ 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] Rb as source for ADEV?
Hi Tom, If I understand you right, the only thing I need from the adev program is the OADEV values and those are the new ADEV? Here's the plot for the past 24 hours using 0 for bins. It takes a few seconds to run, doesn't it? Thanks for the ideas on what to measure. I'm going to replace the EFC divider with low temp coeff resistors and do a software bug fix, and hopefully that will be the end of fiddling with this thing and I'll be able to get some really long runs in. http://www.evoria.net/AE6RV/GPSstd_PLL/Plots/ADEV.2.6.png thanks for all the help, Bob From: Tom Van Baak t...@leapsecond.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, February 6, 2014 5:13 PM Subject: Re: [time-nuts] Rb as source for ADEV? Hi Bob, Short-term measurements like that do a good job using a OCXO and TIC to reveal TIC and GPS resolution limits. It's a useful exercise, but it usually doesn't tell you anything about the OCXO itself. Long-term measurements like that do a superb job using GPS to measure the long-term stability and frequency drift rate of the OCXO (or Rb). This, because for intervals of days to weeks to months you can't beat GPS as an inexpensive ultimate time/frequency standard. And for those long intervals, the TIC resolution is usually more than enough. Just collect the raw phase data and raw DAC data. In a few weeks you'll be able to make some really nice plots. Also consider freezing the DAC for a week (unlocked) and compare that data with your locked data. You can then make plots that look like: http://leapsecond.com/pages/gpsdo/ On Rb -- since you're now a time nut, do not let the Rb warm up at all -- the data get you the first hour or first day will be just as interesting as the data you collect the next month. On ADEV -- I know the source code calls them adev and oadev, but you should just call it ADEV. No one uses the old back-to-back formula anymore; the overlapping formula is the default. And then plot using the all or many tau method I mentioned. /tvb - Original Message - From: Bob Stewart b...@evoria.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, February 06, 2014 2:23 PM Subject: [time-nuts] Rb as source for ADEV? I'm getting a little more familiar with ADEV and OADEV now. With a little help from Tom, I've put together gnuplot scripts and his software to get a decent plot. But, as some time-nuts have pointed out, my measurements are of one part of my system being compared to another. Would I learn anything useful by hooking my Rb standard up to my 5335A and comparing that to the OCXO? How long should I let the Rb heat up before starting the test? I'm a bit uncertain about the result of comparing a stable clock of questionable accuracy to an accurate clock of questionable stability. Hopefully I said that right. thanks, Bob - AE6RV ___ 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] Rb as source for ADEV?
Thanks for the correction. Averaging Time, τ, tau it is. Bob From: Tom Van Baak t...@leapsecond.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, February 6, 2014 9:31 PM Subject: Re: [time-nuts] Rb as source for ADEV? Hi Tom, If I understand you right, the only thing I need from the adev program is the OADEV values and those are the new ADEV? Here's the plot for the past 24 hours using 0 for bins. It takes a few seconds to run, doesn't it? Yes, just grab the code for calc_adev() in http://leapsecond.com/tools/adev_lib.c and always set ovlp = 1. Either way, it's ADEV; it's just that the overlap method gives better results (smaller error bars). http://www.evoria.net/AE6RV/GPSstd_PLL/Plots/ADEV.2.6.png Suggestion: do not label the x-axis time in seconds. This gives the impression that the axis is some sort of elapsed time. Better wording might be integration time, or sampling interval, or averaging time, or tau, or sampling interval, tau. /tvb ___ 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] Rb as source for ADEV?
On 07/02/14 04:22, Tom Van Baak wrote: I never knew about these different versions of ADEV. Can you point me to any reference? Rick Hi Rick, There are a couple of separate issues regarding ADEV. 1) In old literature ADEV was computed using adjacent segments of data. This is about all you could do with a HP 5360A computing counter. Once real computers got into the game, it was possible to use the overlapping version of ADEV, which milks more information from the data set. You can see the two different formulas for computing it at: http://www.wriley.com/paper2ht.htm See calc_adev() source code at: http://leapsecond.com/tools/adev_lib.c Really, the only thing the overlapping version does is use a stride of 1 instead of tau. This is possible when you have the whole data set in memory. The more primitive back-to-back ADEV could be computed as a summing sum, requiring no data storage at all (typical of 60's and 70's instruments). If you read up, you discover that the overlapping trick only came in as an inspiration for ADEV with a pair of articles from J.J. Snyder which took inspiration from ways to get laser frequency estimates quickly. The overlapping technique came to be introduced alongside the tau pre-filtering for the modified Allan Deviation, as can be found in the original MDEV article. 2) Regardless of back-to-back or overlap, there's also the question of how many points to plot. Again, in the early days, because both computation and plotting was very time consuming, people tended to plot only a few points per decade. Maybe tau 1,10,100,1000 or 1,2,5,10,20,50, or 1,2,4,8,16,32, etc. To make it look more like a graph they would connect the dots with lines (and guessing). These days, calculating ADEV is so fast there's no need to even draw the lines; just compute ADEV for every tau you can imagine and the dots connect themselves due to their density. Stable32 has an all tau option in which case ADEV is computed for every possible tau. E.g., 1 to 100,000. However, it turns out this is overkill. Not so much for small tau (say 1 to 100), but once you get up to the thousands or tens of thousands there's usually no significant difference between using tau N and N+1. And it can actually take a lot of time to compute ADEV hundreds of thousands of times. So we are now in the era of many tau which computes lots of tau *per decade*. Think of it as a logarithmic sweep of tau instead of a linear sweep. For large data sets this is orders of magnitude faster than all tau, yet it still fills in all the gaps in the plot with real points, not extrapolated lines. Note that Timelab does many tau by default. 3) And the third issue is, of course, what child in the ADEV family to use: ADEV, MDEV, TDEV, HDEV, etc. Actually, it's not that simple. You actually have a wider palette of selections to choose from: Frequency or time stability - ADEV vs TDEV - a scaling issue Pre-filtering - ADEV vs MDEV - a tau-averaging filter allows better noise separation Derivate processing - ADEV vs HDEV - 2nd vs 3rd phase derivate, higher derivates will surpress more systematic frequency drift components Degrees of Freedom processing - non-overlapping, overlapping, total, theo In principle you can choose algorithm from the full combinatorial matrix, but all the slots isn't filled in, as there is no point in doing non-overlapping MDEV and TDEVs, since overlapping is so simple and gives so good performance. There is no point in doing non-filtered TDEV, as MDEV gives better analysis than ADEV. The scaling is trivial for both. This is to show that the progress of development in these various fields have been on-going. TOTAL and Theo is better in general, but might be more processing than it is worth. I've tried to convey this on the ADEV wikipedia page, but I'm sure it can be improved. Dr. Allan makes the point that one should be using MDEV rather than ADEV, as MDEV was what he wanted ADEV to do, but could not originally, so he was so happy to fix it. I agree with his motivation and analysis. Anyway, what is the problem you are trying to solve? The correct answer depends from case to case. 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.
Re: [time-nuts] Rb as source for ADEV?
On 07/02/14 04:31, Tom Van Baak wrote: Hi Tom, If I understand you right, the only thing I need from the adev program is the OADEV values and those are the new ADEV? Here's the plot for the past 24 hours using 0 for bins. It takes a few seconds to run, doesn't it? Yes, just grab the code for calc_adev() in http://leapsecond.com/tools/adev_lib.c and always set ovlp = 1. Either way, it's ADEV; it's just that the overlap method gives better results (smaller error bars). http://www.evoria.net/AE6RV/GPSstd_PLL/Plots/ADEV.2.6.png Suggestion: do not label the x-axis time in seconds. This gives the impression that the axis is some sort of elapsed time. Better wording might be integration time, or sampling interval, or averaging time, or tau, or sampling interval, tau. Averaging time is unfortunate in several aspects, part for it not being averaging being done and part for the fact that averaging is a separate processing step that can be done, and you can make a plot orthogonal to the ADEV plot with various degrees of averaging-pre-filter. The MDEV uses a tau averaging for a tau observation time. The tau is really the observation time, and ADEV is the frequency stability for that observation time, that is the RMS relative frequency noise when observing it tau seconds later. Similarly the TDEV is the time stability in RMS s for the observation time tau. ADEV also rises for long taus on oscillators, where you expect even better averaging to keep it going further down. The field is confused enough, so I want to avoid this confusion. 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.
Re: [time-nuts] Rb as source for ADEV?
Averaging time is unfortunate in several aspects, part for it not being averaging being done and part for the fact that averaging is a separate processing step that can be done, and you can make a plot orthogonal to the ADEV plot with various degrees of averaging-pre-filter. I agree. The MDEV uses a tau averaging for a tau observation time. The tau is really the observation time, and ADEV is the frequency stability for that observation time, that is the ROMS relative frequency noise when observing it tau seconds later. Similarly the TDEV is the time stability in RMS s for the observation time tau. The phrase observation time is probably no better than averaging time for the x-axis label; they both give the impression of elapsed time to newcomers. Both observation and averaging connote run time or elapsed time or experiment duration. I would stay away from the word time on the ADEV x-axis completely. Using the word interval (as in sampling interval) is good; the least likely to be confused with elapsed time. Also, it's always nice to add tau to the axis label since that letter is universally associated with sampling in TF metrology. Stable32 uses Averaging Time, tau, Seconds. TimeLab avoids the issue by not having labels. /tvb ___ 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] Rb as source for ADEV?
Bob Camp li...@rtty.us: Offset the local reference one hertz or so and let the 5334 do its thing. Any hints on how to get a good oscillator that's off by 1 Hz from 10 MHz? How did you pick 1 Hz? Is 10 Hz offset better? How about 0.1 Hz? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Rb as source for ADEV?
I think I see the problem. I was wondering about using the 1PPS output from my Rb in a test. Cobbling all that together would be a quick bit of work for you, but I spent my life in IT. I'm good with a soldering iron, but I readily admit my shortcomings at hardware tinkering. Bob From: Bob Camp li...@rtty.us To: Tom Van Baak t...@leapsecond.com; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Thursday, February 6, 2014 7:43 PM Subject: Re: [time-nuts] Rb as source for ADEV? Hi My intent was certainly not to stop anybody from doing anything with what they have. My concern is that this is a lot of work for modest return. A simple single mixer setup for $20 would dramatically change things…. $3 mini circuits double balanced mixer $3 op amps x 2 +/- 15 V supply you already have (hopefully). $5 for a piece of perf board $3 for 3 BNC connectors. $3 left over for resistors and capacitors. snip ___ 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] Rb as source for ADEV?
On 07/02/14 03:47, Hal Murray wrote: Bob Camp li...@rtty.us: Offset the local reference one hertz or so and let the 5334 do it’s thing. Any hints on how to get a good oscillator that's off by 1 Hz from 10 MHz? How did you pick 1 Hz? Is 10 Hz offset better? How about 0.1 Hz? Higher beat frequency is better for avoiding flicker noise. Higher beat frequency is better for producing events at higher rate, shorter tau. Lower beat frequency is better for the time-resolution gain (beat/nominal frequency relationship). Higher beat frequency is better for avoiding injection locking. Higher beat frequency makes it easier to make a good noise reduction filter which is stable. There is more, but that should give you a rough hint. Let me know if you need more detailed knowledge on these. 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.
Re: [time-nuts] Rb as source for ADEV?
On 07/02/14 01:09, Richard Karlquist wrote: On 2014-02-06 15:13, Tom Van Baak wrote: On ADEV -- I know the source code calls them adev and oadev, but you should just call it ADEV. No one uses the old back-to-back formula anymore; the overlapping formula is the default. And then plot using the all or many tau method I mentioned. /tvb I never knew about these different versions of ADEV. Can you point me to any reference? Hopefully this is a good start: https://en.wikipedia.org/wiki/Allan_variance In the references I also put NIST SP 1065: http://tf.nist.gov/timefreq/general/pdf/2220.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.
Re: [time-nuts] Rb as source for ADEV?
Hi Tom, If I understand you right, the only thing I need from the adev program is the OADEV values and those are the new ADEV? Here's the plot for the past 24 hours using 0 for bins. It takes a few seconds to run, doesn't it? Yes, just grab the code for calc_adev() in http://leapsecond.com/tools/adev_lib.c and always set ovlp = 1. Either way, it's ADEV; it's just that the overlap method gives better results (smaller error bars). http://www.evoria.net/AE6RV/GPSstd_PLL/Plots/ADEV.2.6.png Suggestion: do not label the x-axis time in seconds. This gives the impression that the axis is some sort of elapsed time. Better wording might be integration time, or sampling interval, or averaging time, or tau, or sampling interval, tau. /tvb ___ 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] Rb as source for ADEV?
I never knew about these different versions of ADEV. Can you point me to any reference? Rick Hi Rick, There are a couple of separate issues regarding ADEV. 1) In old literature ADEV was computed using adjacent segments of data. This is about all you could do with a HP 5360A computing counter. Once real computers got into the game, it was possible to use the overlapping version of ADEV, which milks more information from the data set. You can see the two different formulas for computing it at: http://www.wriley.com/paper2ht.htm See calc_adev() source code at: http://leapsecond.com/tools/adev_lib.c Really, the only thing the overlapping version does is use a stride of 1 instead of tau. This is possible when you have the whole data set in memory. The more primitive back-to-back ADEV could be computed as a summing sum, requiring no data storage at all (typical of 60's and 70's instruments). 2) Regardless of back-to-back or overlap, there's also the question of how many points to plot. Again, in the early days, because both computation and plotting was very time consuming, people tended to plot only a few points per decade. Maybe tau 1,10,100,1000 or 1,2,5,10,20,50, or 1,2,4,8,16,32, etc. To make it look more like a graph they would connect the dots with lines (and guessing). These days, calculating ADEV is so fast there's no need to even draw the lines; just compute ADEV for every tau you can imagine and the dots connect themselves due to their density. Stable32 has an all tau option in which case ADEV is computed for every possible tau. E.g., 1 to 100,000. However, it turns out this is overkill. Not so much for small tau (say 1 to 100), but once you get up to the thousands or tens of thousands there's usually no significant difference between using tau N and N+1. And it can actually take a lot of time to compute ADEV hundreds of thousands of times. So we are now in the era of many tau which computes lots of tau *per decade*. Think of it as a logarithmic sweep of tau instead of a linear sweep. For large data sets this is orders of magnitude faster than all tau, yet it still fills in all the gaps in the plot with real points, not extrapolated lines. Note that Timelab does many tau by default. 3) And the third issue is, of course, what child in the ADEV family to use: ADEV, MDEV, TDEV, HDEV, etc. Does all this make sense? I can post graphic examples of all these issues if you're interested. Thanks, /tvb ___ 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] Rb as source for ADEV?
Hi My intent was certainly not to stop anybody from doing anything with what they have. My concern is that this is a lot of work for modest return. A simple single mixer setup for $20 would dramatically change things…. $3 mini circuits double balanced mixer $3 op amps x 2 +/- 15 V supply you already have (hopefully). $5 for a piece of perf board $3 for 3 BNC connectors. $3 left over for resistors and capacitors. Offset the local reference one hertz or so and let the 5334 do it’s thing. Your resolution is now plenty good enough to see what’s happening. Circuit: Mixer driven by your two sources L/C filter between the mixer output and a positive gain op amp (OP-37 or similar) Op amp set up with enough gain to give you 28V p-p when the mixer is saturated (OP-27 or similar) Next op amp run as an inverter / limiter and driving the counter, use diodes in the feedback path to do the limiting. Not the most elegant circuit. Not the highest resolution possible. Cheap / easy to build / simple to troubleshoot. Used a *lot* of times by a *lot* of people. If you want to get fancy terminate the mixer in 500 ohms at audio and 50 ohms at RF. Fancier still is to do some single pole R-C high pass / low pass in front of the first op-amp. Neither one adds much cost. They do make it slightly harder to build. To totally blow the budget go with an RPD-1 mixer rather than one of the simple ones. Termination would then be 500 ohms at RF and 5K at audio. Bob Yes, I’m assuming you get the mixer at the hamfest / 20 piece price rather than just ordering one at a time from Mine Circuits. On Feb 6, 2014, at 6:52 PM, Tom Van Baak t...@leapsecond.com wrote: Simple answer - doing this directly with a counter is not the best approach. Most of us work with what we have. I think it's pretty cool what Bob is doing with a 5335A. Someday he may buy or build something better. Your best may not be his best, or my best. What is best at one tau is not at another. Time-nuts has never been about being best (otherwise we all loose to USNO); it's about learning and exploring this interesting field of time frequency with what we have at home, whether it's the ADEV of 60 Hz or ADEV of a 5335A/GPSDO, etc. /tvb ___ 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] Rb as source for ADEV?
To add a bit to this discussion I recently switched from using from using HP5370B's for long term data collection to HP5335's. For plotting the long term drift of two of my more stable OCXO's versus a GPSDO the 5335's combined with Timelab work fine for my limited needs. Just for grins I compared the same sources using both the 5370B's and the 5335's at the same time and overlaid the ADEV plots, IIRC the results were identical for Tau's of approx 2,000 seconds and higher. At times I also compare the OCXO's to one of my better Rb's (while also comparing the OCXO's to the GPSDO) to provide a bit of a sanity check that the GPSDO is behaving itself. I also wrote data collection routines using that time stamp all of the data I collect which makes later comparisions considerably easier. Regards Mark S ___ 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] Rb as source for ADEV?
On 07/02/14 05:27, Tom Van Baak wrote: Averaging time is unfortunate in several aspects, part for it not being averaging being done and part for the fact that averaging is a separate processing step that can be done, and you can make a plot orthogonal to the ADEV plot with various degrees of averaging-pre-filter. I agree. The MDEV uses a tau averaging for a tau observation time. The tau is really the observation time, and ADEV is the frequency stability for that observation time, that is the ROMS relative frequency noise when observing it tau seconds later. Similarly the TDEV is the time stability in RMS s for the observation time tau. The phrase observation time is probably no better than averaging time for the x-axis label; they both give the impression of elapsed time to newcomers. Both observation and averaging connote run time or elapsed time or experiment duration. I would stay away from the word time on the ADEV x-axis completely. Using the word interval (as in sampling interval) is good; the least likely to be confused with elapsed time. Also, it's always nice to add tau to the axis label since that letter is universally associated with sampling in TF metrology. Stable32 uses Averaging Time, tau, Seconds. TimeLab avoids the issue by not having labels. Observation time is better, but it needs to be used properly not to be confused with measurement time. You can never make a single term become completely unambiguous from all interpretations, rather you pick one and define what it means and stick with it. Observation period is what I've used in the ADEV wiki. Avoids time as it is often confused for elapsed measurement time. Stable32 and SP 1065 (both by W. Riley) uses the loose term Averaging time, as that is what it was called initially, before the analysis became more complex and they needed to separate terms. 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.
Re: [time-nuts] Rb as source for ADEV?
Hi Hal, More offset is better, but the actual amount is irrelevent. It's easier to process the difference frequency (i.e. 1 Hz or 10 Hz or whatever) if it's higher. The problem is that low frequency means low slew rate which means trigger noise that will be interpreted as jitter which will mess up your results. However, it's not easy to find high quality oscillators that are slightly offset from the standard frequencies. For some technologies you may not be able to move the frequencies by any significant amount. You can use a synthesizer to generate an offset frequency, but that has to be done carefully to ensure that the synthesizer doesn't inject a bunch of noise into the measurement. The big boys tend to avoid these issues by using a DMTD (Dual Mixer, Time Difference) method, but that's not a reasonable solution for a beginner. A typical progression for a new time nut is to start with a TIC (Time Interval Counter) and make measurements as described earlier in this thread. Maybe upgrade your TIC once or twice. Then, as the time nut infection settles into your bones and soul, move on to the mixer and eventually to the DMTD as you make measurements at lower and lower levels. You also tend to upgrade your references on a more or less continuous basis. Speaking of the infection settling into your bones, a few months ago I thought my pulse was oddly low. I looked over at my WWVB analog clock and found that not only was my pulse 60 beats per minute, but it was also in sync with the second hand of the clock! I've got it bad! Ed On 2/6/2014 8:47 PM, Hal Murray wrote: Bob Camp li...@rtty.us: Offset the local reference one hertz or so and let the 5334 do it’s thing. Any hints on how to get a good oscillator that's off by 1 Hz from 10 MHz? How did you pick 1 Hz? Is 10 Hz offset better? How about 0.1 Hz? ___ 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.
