Hi > On Apr 14, 2020, at 11:01 AM, Tobias Pluess <tpluess@ieee.org> wrote: > > Hi Bob > > yes I totally agree, you can save a lot of space by having those USB boxes > for almost every measurement. > However I am happy that we have at work the "old school stuff" (by which I > don't mean we have old equipment, actually it is pretty modern) because in > my opinion the user experience is much better if you have buttons to press > and knobs to rotate. I don't like the scopes where you have to set up > everything via touchscreen, and I don't like the USB scopes. Therefore I am > actually quite happy with the kind of equipment that sits in its own box, > the disadvantage is that it needs space. However I think this is only a > concern for the homelab, where space is limited. A place where they don't > have the space to install a proper network analyzer is perhaps a bit ... > funny, I'd say. But for home usage you're probably right. However many of > the USB things have lots of drawbacks the "pro" equipment doesn't have. But > perhaps we are wandering off the subject a bit now :-) I have more space on my home bench than I did on any bench at any place I ever worked. I have never worked at a location (or visited one) where full sized / old style network analyzers were deployed to all dozen or three engineering benches. Same thing with 3048 style phase noise test sets. For phase noise, the issue was spur pickup as much as anything else. The USB stuff actually is *better* than the old gear in that regard. > >> Lots of projects started and never fully completed. I have piles and > piles of them …. > > yeah I know. I have them as well. Not piles, but certainly quite a few. But > I have also piles of stuff I have finished. For instance from time to time > I try to manufacture RF waveguide components like directional couplers and > bandpass filters and the like. While I don't actually need them I simply > want to see whether I could make them and how precise it is possible. (it > is possible quite accurately up to perhaps 80GHz, above that precision > becomes an issue). And as you know especially the waveguide stuff is bulky > :-) I even once made my own N connectors just to see whether it was > possible. (it is, as well. When gold plated or at least polished, they look > very similar to the commercial ones.) > > But this is definitely seriously off-topic ;-) To ask a back-to-topic > question: you said you wrote your own programs to extract ADEV from > timetagged data. Could you give a hint on how you "massage" (as you said) > the data from the time tagger to get proper phase info and ADEV? I wrote the first stuff back in the 70’s. It got redone several times as I moved from plant to plant over the years. By the late 90’s these systems began to fade out in industry. Normally the code looks for jumps and then makes arbitrary decisions about how to “patch” them. With a time tagger, most of the problems are actually dropouts in the data. How you fill those depends on what you are doing ( you may re-do the run ). Simply putting in the phase data from the previous point is an alternative. Bob > > Tobias > > > On Tue, Apr 14, 2020 at 2:51 PM Bob kb8tq <kb8tq@n1k.org> wrote: > >> Hi >> >> The whole “volume of clutter” on the desk / bench / around the lab / >> basement >> is one of the many drivers getting me to move over to some of the more >> modern USB based measurement gear. You can swap out 400 lb of cranky >> (but useful ) gear from the 1960’s for what would fit in a small >> backpack. >> >> Even at work, the same sort of drivers applied. A USB based box was >> something >> that you could have a dozen of out on many benches. The big beast setup >> hulked >> away on it’s own bench over in the corner. A lot more got done with the >> little boxes. >> >> There are a lot of grades of USB gear. I’m not suggesting that my $100 >> network >> analyzer competes for accuracy with a shiny new R&S or Keysight device. It >> just >> *might* do as good a job as the broken down pile of gear from 1968 though. >> For >> a bit more than $100, I could get a better USB version …. >> >> ===== >> >> Can you build your own TICC / scope / network analyzer / PC / television? >> Sure you can. It’s just parts put together in this or that fashion. >> Getting one to the >> point that it measures up with what you can buy will take a while (likely >> a couple >> of passes). >> >> Your time is “free" since this is a hobby. Does that really include 40 >> hours a week >> for a year to get this or that pass done? At least to me … nope. How about >> the lab >> full of application specific test gear to get this piece of gear debugged >> *before* you >> can use it ? Hmmm…. >> >> Simply getting the board laid out is the easy part of any of this. On a >> normal >> product design, the work to get to that point is maybe 10% of the effort >> put in >> to get the job done. A home project may be even more lopsided since it >> likely >> is the first time you have done this or that. >> >> Lots of twists and turns. Lots of projects started and never fully >> completed. >> I have piles and piles of them …. >> >> Bob >> >>> On Apr 14, 2020, at 8:15 AM, Tobias Pluess <tpluess@ieee.org> wrote: >>> >>> Hi Bob >>> yes sure I know. At least my homebrew GPSDO and the STAR4 GPSDO I have >> are >>> always powered, but since they don't take much space on my desk that's >>> okay. But for the signal generators (or SpecAn etc) it is a completely >>> different story; I usually take them from the shelf when I need them and >>> put them back afterwards, because they simply take too much space away. >> And >>> my home lab has only limited space, unfortunately. I am thinking since >>> months about a better setup (how arrange everything, how to stack my >>> equipment and such) but it is not so easy because simply stacking all >>> equipment on top of each other is unsatisfactory (in that case one needs >> in >>> general the instrument at the very top, which is simply too far away >> :-)). >>> The 8663A is a nice machine, but it would fill my desk already by 50%, so >>> no way to leave it there (and therefore I cannot keep it powered). >>> >>> Tobias >>> >>> >>> On Tue, Apr 14, 2020 at 1:54 PM Bob kb8tq <kb8tq@n1k.org> wrote: >>> >>>> Hi >>>> >>>>> On Apr 14, 2020, at 2:31 AM, Tobias Pluess <tpluess@ieee.org> wrote: >>>>> >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there.

On Tuesday, April 14, 2020, 7:48:34 AM EDT, Bob kb8tq <kb8tq@n1k.org> wrote:  

Bob, Tobias, et al TICC (TAPR) isn't problem free either.  It has a tendency to get TimeLab confused on data from port A and port B.  The data stream has identifier on them but TimeLab discards it.  Then it expects A and B comes alternately.  I communicated with both developers but for time being, the solution is to record the data and inspect. --------------------------------------- (Mr.) Taka Kamiya KB4EMF / ex JF2DKG On Tuesday, April 14, 2020, 7:48:34 AM EDT, Bob kb8tq <kb8tq@n1k.org> wrote: Hi If the phase slips are “well behaved” they can be handled. The problem with a dual channel setup is that they are often not well behaved.  The period is 100 ns so a frequency drift of 1 ppb will put you in trouble in under 2 minutes. The only real answer is to do it properly and time tag the two outputs. Any other approach will get you yelling and screaming at the test set. Playing with two counters and not time tagging is in the “yelling and screaming” category as well. Get a TAPPR TICC if you really want to do a DMTD. Of course you *could* just use a single mixer. That works fine with the counter you already have. It will give you an A to B test just like a DMTD. The only limitation is the need to tune at least one of the oscillators in each pair. There is no requirement that you tune only one. If both are tunable, you could tune one to the high end of its range and the other to the low end. With most OCXO’s, there is plenty of tune range. Bob > On Apr 14, 2020, at 2:23 AM, Tobias Pluess <tpluess@ieee.org> wrote: > > Hey Bob > > ok now I see your point! you talk about the phase spillovers. Timelab and > also Stable32 can correct for them, so it shouldn't be a problem, right? > > But I agree, if you cannot correct for the spillovers it becomes even more > difficult. > > > Tobias > > On Tue., 14 Apr. 2020, 01:38 Bob kb8tq, <kb8tq@n1k.org> wrote: > >> Hi >> >> The gotcha with using a conventional counter (as opposed to a time tagger) >> is that you never know when things are going to “slip” past each other. >> When they >> do you get a major burp in your data. Bill’s setup is running a time >> tagger …. >> >> ( = It runs an internal time count, each edge gets “labeled” with a >> precise time >> stamp that is good to nanoseconds or picoseconds. A Time Interval Counter >> simply measures the time between edges. That sounds like the same thing, >> but >> it’s not quite ….) >> >> >>> On Apr 13, 2020, at 6:11 PM, Tobias Pluess <tpluess@ieee.org> wrote: >>> >>> Hi Bob >>> >>> Riley suggests to use a single TIC >>> >>> http://wriley.com/A%20Small%20DMTD%20System.pdf >>> >>> when you look at the block diagram Fig. 4, you can see that one TIC >> allows >>> to compare two oscillators. >>> I don't know exactly how, though :-) >> >> The gotcha with using a conventional counter (as opposed to a time tagger) >> is that you never know when things are going to “slip” past each other. >> When they >> do you get a major burp in your data. Bill’s setup is running a time >> tagger …. >> >>> >>> OK and I see your point on the 8663. I will try to use another reference! >>> I definitely didn't keep mine on for a long time. I didn't use the signal >>> generator for a while now, so it was unplugged for a few months. I assume >>> that's far from optimal for the 10811's stability. >> >> Best approach is to mount your reference off on it’s own and just power >> it. That way >> you don’t wear out all the guts of a fancy piece of gear. >> >> Bob >> >>> >>> >>> Tobias >>> >>> >>> >>> On Mon., 13 Apr. 2020, 23:53 Bob kb8tq, <kb8tq@n1k.org> wrote: >>> >>>> Hi >>>> >>>>> On Apr 13, 2020, at 5:06 PM, Tobias Pluess <tpluess@ieee.org> wrote: >>>>> >>>>> Hi Bob >>>>> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-) >>>>> >>>>> Maybe I have some good OpAmps for this purpose in my box. I will try >> it! >>>> of >>>> >>>> You need something that is quiet (like the OP-37) and has a pretty good >>>> slew >>>> rate. Past that, there are a lot of candidates. The TI OPA-228 family is >>>> one. >>>> >>>>> course I saw that my setup was not ideal as there was a bit of noise on >>>> the >>>>> signals which I guess does lead to some jitter in the trigger circuit >> and >>>>> therefore decreases my measurement noise floor. >>>> >>>> Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good >>>> digits. >>>> Net result is a measurement that’s good in the vicinity of parts in >> 10^-13 >>>> >>>>> >>>>> Can you say something about how it would be done using a TIC? >>>>> I don't have two identically good counters, but the HP 5335A could be >>>> used >>>>> as TIC, couldn't it. >>>> >>>> The standard way of doing the test is to run two counters / two TIC/s / >>>> two whatever’s. >>>> I know of no practical way to do it with a single 5335. >>>> >>>>> >>>>> And the offset source I used is not directly the HP 10811, but the HP >>>> 8663A >>>>> Signal generator internally uses a 10811 as reference source. But I >>>> didn't >>>>> wait for days for it to warm up properly. (Should I?) >>>> >>>> The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of >> how >>>> you >>>> use the 10811, it needs to be on for a while. How long very much depends >>>> on >>>> just how long it’s been off. Best to keep it on all the time. >>>> >>>>> >>>>>> Fun !!! >>>>> Yea, of course! :-) >>>>> I already implemented the ADEV, MDEV and TDEV calculations in Matlab by >>>>> myself. I use TimeLab to see what numbers I should expect, and then I >>>> want >>>>> to compute it all myself in Matlab because I want to see how it >> actually >>>>> works. ;-) >>>> >>>> Be careful any time you code this stuff for the first time. It’s >> amazingly >>>> easy >>>> ( = I’ve done it ….) to make minor errors. That’s in no way to suggest >> that >>>> you should not code it up yourself. I generally do it in Excel or in C. >>>> >>>> Bob >>>> >>>>> >>>>> >>>>> Best >>>>> Tobias >>>>> >>>>> >>>>> >>>>> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq <kb8tq@n1k.org> wrote: >>>>> >>>>>> Hi >>>>>> >>>>>> Ok, first the math: >>>>>> >>>>>> If your offset oscillator is 10 Hz high at 10 MHz, you have a: >>>>>> >>>>>> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD >>>>>> >>>>>> You get to add a 6 to what Time Lab shows you. >>>>>> >>>>>> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier >>>>>> gets you to 1x10^-10 >>>>>> >>>>>> So, what’s going on? >>>>>> >>>>>> You can’t feed the mixer outputs straight into a counter. The counter >>>>>> front >>>>>> end does not handle LF audio sine waves very well. You need to do an >>>>>> op-amp based limiter. A pair of OP-37’s in each leg ( or something >>>>>> similar) >>>>>> should do the trick. >>>>>> >>>>>> Second, the offset source needs to be pretty good. A 10811 tuned high >>>> with >>>>>> both the mechanical trim and the EFC is a pretty good choice to start >>>> out. >>>>>> >>>>>> If you only have one counter, simply ignore the second channel. You >> are >>>> now >>>>>> running a single mixer. It still works as a comparison between the >>>> offset >>>>>> oscillator >>>>>> and your DUT. >>>>>> >>>>>> If you want to do it properly as a DMTD, then you set up two counters. >>>> One >>>>>> to measure mixer A and the other to measure mixer B.  Set them both up >>>> to >>>>>> measure frequency. Time tag the data files so you know which reading >>>>>> matches up with which. >>>>>> >>>>>> Fun !!! >>>>>> >>>>>> Bob >>>>>> >>>>>>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess <tpluess@ieee.org> wrote: >>>>>>> >>>>>>> Hi again Bob >>>>>>> >>>>>>> I tried to do some measurements with a DMTD! >>>>>>> In my junk box I found a little PCB from earlier experiments on that >>>>>> topic, >>>>>>> with a power splitter and two SRA-3H mixers, it was even already >> wired >>>>>> for >>>>>>> the DMTD configuration. So I gave it a try! >>>>>>> As "transfer oscillator" I used my HP 8663A signal generator, and set >>>> it >>>>>>> high in frequency by 10 Hz. To the two mixers, I connected the two >>>> 10MHz >>>>>>> signals and at the mixer outputs, I put a little lowpass filter with >>>>>> 100Hz >>>>>>> corner frequency. >>>>>>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I >>>>>> tried >>>>>>> to feed them directly into the HP 5335A TIC and used the TI mode to >>>>>> measure >>>>>>> the delay between the two signals. >>>>>>> This gives 10 readings/sec, which I try to process with TimeLab. >>>>>>> It does give some interesting graphs, but I don't know yet how to >>>>>> correctly >>>>>>> set up TimeLab for this kind of measurement. I.e. now, I get an ADEV >> in >>>>>> the >>>>>>> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that >> mean >>>> I >>>>>>> simply need to multiply this with 1e-7 to get the *real* ADEV at >> 10MHz? >>>>>>> this would mean that my real ADEV is in the range of 1e-11 to 1e-12, >>>>>> which >>>>>>> is indeed my target value, BUT I expect that things are not that >>>> simple. >>>>>>> (i.e. what if I didn't set the transfer oscillator high by +10Hz but >>>> only >>>>>>> by 9.9Hz for example). >>>>>>> Can you give some hints on that? >>>>>>> Of course I also did the noise floor test (i.e. I fed the 10MHz >> signal >>>>>> into >>>>>>> a power splitter and connected the two outputs to my DMTD with two >>>>>>> different lenghts of cables. This gave results starting at 1e-4 going >>>>>> down >>>>>>> to 1e-7, maybe it would have gone even lower but I measured only for >> a >>>>>>> couple of minutes.) >>>>>>> >>>>>>> Can you give some hints on that? >>>>>>> >>>>>>> Best >>>>>>> Tobias >>>>>>> HB9FSX >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq <kb8tq@n1k.org> wrote: >>>>>>>> >>>>>>>>> Hi >>>>>>>>> >>>>>>>>> The quick way to do this is with a single mixer. Take something >> like >>>> an >>>>>>>>> old >>>>>>>>> 10811 and use the coarse tune to set it high in frequency by 5 to >> 10 >>>>>> Hz. >>>>>>>>> >>>>>>>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio >>>>>> tone. >>>>>>>>> That tone is the *difference* between the 10811 and your device >> under >>>>>>>>> test. >>>>>>>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz. >>>>>>>>> >>>>>>>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very >>>> small >>>>>>>>> shift >>>>>>>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the >>>>>> change >>>>>>>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X >>>> increase >>>>>> ). >>>>>>>>> >>>>>>>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no, >> it’s >>>>>> not >>>>>>>>> that >>>>>>>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1 >>>>>>>>> second. >>>>>>>>> >>>>>>>>> The reason its not quite that simple is that the input circuit on >> the >>>>>>>>> counter >>>>>>>>> really does not handle a 10 Hz audio tone as well as it handles a >> 10 >>>>>> MHz >>>>>>>>> RF signal. Instead of getting 9 digits a second, you probably will >>>> get >>>>>>>>> three >>>>>>>>> *good* digits a second and another 6 digits of noise. >>>>>>>>> >>>>>>>>> The good news is that an op amp used as a preamp ( to get you up to >>>>>> maybe >>>>>>>>> 32 V p-p rather than a volt or so) and another op amp or three as >>>>>>>>> limiters will >>>>>>>>> get you up around 6 or 7 good digits. Toss in a cap or two as a >> high >>>>>> pass >>>>>>>>> and low pass filter ( DC offsets can be a problem ….) and you have >> a >>>>>>>>> working >>>>>>>>> device that gets into the parts in 10^-13 with your 5335. >>>>>>>>> >>>>>>>>> It all can be done with point to point wiring. No need for a PCB >>>>>> layout. >>>>>>>>> Be >>>>>>>>> careful that the +/- 18V supplies to the op amp *both* go on and >> off >>>> at >>>>>>>>> the >>>>>>>>> same time …. >>>>>>>>> >>>>>>>>> Bob >>>>>>>>> >>>>>>>> >>>>>>> _______________________________________________ >>>>>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>>>>> To unsubscribe, go to >>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>>>> and follow the instructions there. >>>>>> >>>>>> >>>>>> _______________________________________________ >>>>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>>>> To unsubscribe, go to >>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>>> and follow the instructions there. >>>>>> >>>>> _______________________________________________ >>>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>>> To unsubscribe, go to >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>> and follow the instructions there. >>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>> To unsubscribe, go to >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>> and follow the instructions there. >>>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@lists.febo.com >>> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.

On Tuesday, April 14, 2020, 7:48:34 AM EDT, Bob kb8tq <kb8tq@n1k.org> wrote:  

Hi Have you tried it with the latest firmware update? I’ve never seen the problem here. Bob > On Apr 14, 2020, at 1:05 PM, Taka Kamiya via time-nuts <time-nuts@lists.febo.com> wrote: > > Bob, Tobias, et al > > TICC (TAPR) isn't problem free either. It has a tendency to get TimeLab confused on data from port A and port B. The data stream has identifier on them but TimeLab discards it. Then it expects A and B comes alternately. I communicated with both developers but for time being, the solution is to record the data and inspect. > > --------------------------------------- > (Mr.) Taka Kamiya > KB4EMF / ex JF2DKG > > > On Tuesday, April 14, 2020, 7:48:34 AM EDT, Bob kb8tq <kb8tq@n1k.org> wrote: > > Hi > > If the phase slips are “well behaved” they can be handled. The problem > with a dual channel setup is that they are often not well behaved. The > period is 100 ns so a frequency drift of 1 ppb will put you in trouble in > under 2 minutes. > > The only real answer is to do it properly and time tag the two outputs. > Any other approach will get you yelling and screaming at the test set. > Playing with two counters and not time tagging is in the “yelling and > screaming” category as well. > > Get a TAPPR TICC if you really want to do a DMTD. > > Of course you *could* just use a single mixer. That works fine with the > counter you already have. It will give you an A to B test just like a > DMTD. The only limitation is the need to tune at least one of the oscillators > in each pair. > > There is no requirement that you tune only one. If both are tunable, > you could tune one to the high end of its range and the other to the low end. > With most OCXO’s, there is plenty of tune range. > > Bob > >> On Apr 14, 2020, at 2:23 AM, Tobias Pluess <tpluess@ieee.org> wrote: >> >> Hey Bob >> >> ok now I see your point! you talk about the phase spillovers. Timelab and >> also Stable32 can correct for them, so it shouldn't be a problem, right? >> >> But I agree, if you cannot correct for the spillovers it becomes even more >> difficult. >> >> >> Tobias >> >> On Tue., 14 Apr. 2020, 01:38 Bob kb8tq, <kb8tq@n1k.org> wrote: >> >>> Hi >>> >>> The gotcha with using a conventional counter (as opposed to a time tagger) >>> is that you never know when things are going to “slip” past each other. >>> When they >>> do you get a major burp in your data. Bill’s setup is running a time >>> tagger …. >>> >>> ( = It runs an internal time count, each edge gets “labeled” with a >>> precise time >>> stamp that is good to nanoseconds or picoseconds. A Time Interval Counter >>> simply measures the time between edges. That sounds like the same thing, >>> but >>> it’s not quite ….) >>> >>> >>>> On Apr 13, 2020, at 6:11 PM, Tobias Pluess <tpluess@ieee.org> wrote: >>>> >>>> Hi Bob >>>> >>>> Riley suggests to use a single TIC >>>> >>>> http://wriley.com/A%20Small%20DMTD%20System.pdf >>>> >>>> when you look at the block diagram Fig. 4, you can see that one TIC >>> allows >>>> to compare two oscillators. >>>> I don't know exactly how, though :-) >>> >>> The gotcha with using a conventional counter (as opposed to a time tagger) >>> is that you never know when things are going to “slip” past each other. >>> When they >>> do you get a major burp in your data. Bill’s setup is running a time >>> tagger …. >>> >>>> >>>> OK and I see your point on the 8663. I will try to use another reference! >>>> I definitely didn't keep mine on for a long time. I didn't use the signal >>>> generator for a while now, so it was unplugged for a few months. I assume >>>> that's far from optimal for the 10811's stability. >>> >>> Best approach is to mount your reference off on it’s own and just power >>> it. That way >>> you don’t wear out all the guts of a fancy piece of gear. >>> >>> Bob >>> >>>> >>>> >>>> Tobias >>>> >>>> >>>> >>>> On Mon., 13 Apr. 2020, 23:53 Bob kb8tq, <kb8tq@n1k.org> wrote: >>>> >>>>> Hi >>>>> >>>>>> On Apr 13, 2020, at 5:06 PM, Tobias Pluess <tpluess@ieee.org> wrote: >>>>>> >>>>>> Hi Bob >>>>>> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-) >>>>>> >>>>>> Maybe I have some good OpAmps for this purpose in my box. I will try >>> it! >>>>> of >>>>> >>>>> You need something that is quiet (like the OP-37) and has a pretty good >>>>> slew >>>>> rate. Past that, there are a lot of candidates. The TI OPA-228 family is >>>>> one. >>>>> >>>>>> course I saw that my setup was not ideal as there was a bit of noise on >>>>> the >>>>>> signals which I guess does lead to some jitter in the trigger circuit >>> and >>>>>> therefore decreases my measurement noise floor. >>>>> >>>>> Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good >>>>> digits. >>>>> Net result is a measurement that’s good in the vicinity of parts in >>> 10^-13 >>>>> >>>>>> >>>>>> Can you say something about how it would be done using a TIC? >>>>>> I don't have two identically good counters, but the HP 5335A could be >>>>> used >>>>>> as TIC, couldn't it. >>>>> >>>>> The standard way of doing the test is to run two counters / two TIC/s / >>>>> two whatever’s. >>>>> I know of no practical way to do it with a single 5335. >>>>> >>>>>> >>>>>> And the offset source I used is not directly the HP 10811, but the HP >>>>> 8663A >>>>>> Signal generator internally uses a 10811 as reference source. But I >>>>> didn't >>>>>> wait for days for it to warm up properly. (Should I?) >>>>> >>>>> The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of >>> how >>>>> you >>>>> use the 10811, it needs to be on for a while. How long very much depends >>>>> on >>>>> just how long it’s been off. Best to keep it on all the time. >>>>> >>>>>> >>>>>>> Fun !!! >>>>>> Yea, of course! :-) >>>>>> I already implemented the ADEV, MDEV and TDEV calculations in Matlab by >>>>>> myself. I use TimeLab to see what numbers I should expect, and then I >>>>> want >>>>>> to compute it all myself in Matlab because I want to see how it >>> actually >>>>>> works. ;-) >>>>> >>>>> Be careful any time you code this stuff for the first time. It’s >>> amazingly >>>>> easy >>>>> ( = I’ve done it ….) to make minor errors. That’s in no way to suggest >>> that >>>>> you should not code it up yourself. I generally do it in Excel or in C. >>>>> >>>>> Bob >>>>> >>>>>> >>>>>> >>>>>> Best >>>>>> Tobias >>>>>> >>>>>> >>>>>> >>>>>> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq <kb8tq@n1k.org> wrote: >>>>>> >>>>>>> Hi >>>>>>> >>>>>>> Ok, first the math: >>>>>>> >>>>>>> If your offset oscillator is 10 Hz high at 10 MHz, you have a: >>>>>>> >>>>>>> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD >>>>>>> >>>>>>> You get to add a 6 to what Time Lab shows you. >>>>>>> >>>>>>> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier >>>>>>> gets you to 1x10^-10 >>>>>>> >>>>>>> So, what’s going on? >>>>>>> >>>>>>> You can’t feed the mixer outputs straight into a counter. The counter >>>>>>> front >>>>>>> end does not handle LF audio sine waves very well. You need to do an >>>>>>> op-amp based limiter. A pair of OP-37’s in each leg ( or something >>>>>>> similar) >>>>>>> should do the trick. >>>>>>> >>>>>>> Second, the offset source needs to be pretty good. A 10811 tuned high >>>>> with >>>>>>> both the mechanical trim and the EFC is a pretty good choice to start >>>>> out. >>>>>>> >>>>>>> If you only have one counter, simply ignore the second channel. You >>> are >>>>> now >>>>>>> running a single mixer. It still works as a comparison between the >>>>> offset >>>>>>> oscillator >>>>>>> and your DUT. >>>>>>> >>>>>>> If you want to do it properly as a DMTD, then you set up two counters. >>>>> One >>>>>>> to measure mixer A and the other to measure mixer B. Set them both up >>>>> to >>>>>>> measure frequency. Time tag the data files so you know which reading >>>>>>> matches up with which. >>>>>>> >>>>>>> Fun !!! >>>>>>> >>>>>>> Bob >>>>>>> >>>>>>>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess <tpluess@ieee.org> wrote: >>>>>>>> >>>>>>>> Hi again Bob >>>>>>>> >>>>>>>> I tried to do some measurements with a DMTD! >>>>>>>> In my junk box I found a little PCB from earlier experiments on that >>>>>>> topic, >>>>>>>> with a power splitter and two SRA-3H mixers, it was even already >>> wired >>>>>>> for >>>>>>>> the DMTD configuration. So I gave it a try! >>>>>>>> As "transfer oscillator" I used my HP 8663A signal generator, and set >>>>> it >>>>>>>> high in frequency by 10 Hz. To the two mixers, I connected the two >>>>> 10MHz >>>>>>>> signals and at the mixer outputs, I put a little lowpass filter with >>>>>>> 100Hz >>>>>>>> corner frequency. >>>>>>>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I >>>>>>> tried >>>>>>>> to feed them directly into the HP 5335A TIC and used the TI mode to >>>>>>> measure >>>>>>>> the delay between the two signals. >>>>>>>> This gives 10 readings/sec, which I try to process with TimeLab. >>>>>>>> It does give some interesting graphs, but I don't know yet how to >>>>>>> correctly >>>>>>>> set up TimeLab for this kind of measurement. I.e. now, I get an ADEV >>> in >>>>>>> the >>>>>>>> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that >>> mean >>>>> I >>>>>>>> simply need to multiply this with 1e-7 to get the *real* ADEV at >>> 10MHz? >>>>>>>> this would mean that my real ADEV is in the range of 1e-11 to 1e-12, >>>>>>> which >>>>>>>> is indeed my target value, BUT I expect that things are not that >>>>> simple. >>>>>>>> (i.e. what if I didn't set the transfer oscillator high by +10Hz but >>>>> only >>>>>>>> by 9.9Hz for example). >>>>>>>> Can you give some hints on that? >>>>>>>> Of course I also did the noise floor test (i.e. I fed the 10MHz >>> signal >>>>>>> into >>>>>>>> a power splitter and connected the two outputs to my DMTD with two >>>>>>>> different lenghts of cables. This gave results starting at 1e-4 going >>>>>>> down >>>>>>>> to 1e-7, maybe it would have gone even lower but I measured only for >>> a >>>>>>>> couple of minutes.) >>>>>>>> >>>>>>>> Can you give some hints on that? >>>>>>>> >>>>>>>> Best >>>>>>>> Tobias >>>>>>>> HB9FSX >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq <kb8tq@n1k.org> wrote: >>>>>>>>> >>>>>>>>>> Hi >>>>>>>>>> >>>>>>>>>> The quick way to do this is with a single mixer. Take something >>> like >>>>> an >>>>>>>>>> old >>>>>>>>>> 10811 and use the coarse tune to set it high in frequency by 5 to >>> 10 >>>>>>> Hz. >>>>>>>>>> >>>>>>>>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio >>>>>>> tone. >>>>>>>>>> That tone is the *difference* between the 10811 and your device >>> under >>>>>>>>>> test. >>>>>>>>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz. >>>>>>>>>> >>>>>>>>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very >>>>> small >>>>>>>>>> shift >>>>>>>>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the >>>>>>> change >>>>>>>>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X >>>>> increase >>>>>>> ). >>>>>>>>>> >>>>>>>>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no, >>> it’s >>>>>>> not >>>>>>>>>> that >>>>>>>>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1 >>>>>>>>>> second. >>>>>>>>>> >>>>>>>>>> The reason its not quite that simple is that the input circuit on >>> the >>>>>>>>>> counter >>>>>>>>>> really does not handle a 10 Hz audio tone as well as it handles a >>> 10 >>>>>>> MHz >>>>>>>>>> RF signal. Instead of getting 9 digits a second, you probably will >>>>> get >>>>>>>>>> three >>>>>>>>>> *good* digits a second and another 6 digits of noise. >>>>>>>>>> >>>>>>>>>> The good news is that an op amp used as a preamp ( to get you up to >>>>>>> maybe >>>>>>>>>> 32 V p-p rather than a volt or so) and another op amp or three as >>>>>>>>>> limiters will >>>>>>>>>> get you up around 6 or 7 good digits. Toss in a cap or two as a >>> high >>>>>>> pass >>>>>>>>>> and low pass filter ( DC offsets can be a problem ….) and you have >>> a >>>>>>>>>> working >>>>>>>>>> device that gets into the parts in 10^-13 with your 5335. >>>>>>>>>> >>>>>>>>>> It all can be done with point to point wiring. No need for a PCB >>>>>>> layout. >>>>>>>>>> Be >>>>>>>>>> careful that the +/- 18V supplies to the op amp *both* go on and >>> off >>>>> at >>>>>>>>>> the >>>>>>>>>> same time …. >>>>>>>>>> >>>>>>>>>> Bob >>>>>>>>>> >>>>>>>>> >>>>>>>> _______________________________________________ >>>>>>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>>>>>> To unsubscribe, go to >>>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>>>>> and follow the instructions there. >>>>>>> >>>>>>> >>>>>>> _______________________________________________ >>>>>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>>>>> To unsubscribe, go to >>>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>>>> and follow the instructions there. >>>>>>> >>>>>> _______________________________________________ >>>>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>>>> To unsubscribe, go to >>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>>> and follow the instructions there. >>>>> >>>>> >>>>> _______________________________________________ >>>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>>> To unsubscribe, go to >>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>> and follow the instructions there. >>>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>> To unsubscribe, go to >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>> and follow the instructions there. >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@lists.febo.com >>> To unsubscribe, go to >>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >>> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there.

On Tuesday, April 14, 2020, 7:48:34 AM EDT, Bob kb8tq <kb8tq@n1k.org> wrote:  

It's a feature not a bug. :-) I was going to address possible out-of-sequence output in this update, but after lots and lots of thinking and experiments, and discussions with a few bright folks on this list, I've come to the conclusion that there is no 100% reliable way to do sample ordering within the TICC, unless you provide it with additional information about the test configuration and guarantee the integrity of the incoming signals. It seems trivial to just sort samples if you make some assumptions: that both channels are providing data at the same rate, that neither one will ever glitch, and that both of them will always be present. But... what if chA is at 1 PPS and chB is at 10 PPS? What if you're only measuring one channel? Those could be solved by telling the TICC what the configuration is, or doing some sort of signal analysis at the start of the run, but that adds a lot of complexity to the code (and operation). And then, what if chA goes away during the measurement but chB keeps on ticking? What if one of the DUTs glitches so there is a missing sample? Or an extra one? Those occurrences will screw up any attempt at sequencing. Apart from that, there is a subtle quirk in the TICC architecture (thanks to TVB for spotting this) -- because of the way the TDC7200 chip works, if a sample arrives on each input nearly simultaneously, you cannot tell which one occurred first until *after* both samples are processed. Because there are non-deterministic latencies in the processing loop, there can be a situation where, for example, chB has a slightly earlier timestamp but is processed after chA. So you can get an output file where the timestamps are not always in ascending order. I was originally going to say that addressing this particular problem in the firmware would be sensitive to all the gotchas mentioned in the previous paragraphs. But as I was typing I realized that there might be a fairly simple way to guarantee that the output is at least in increasing-timestamp order. That doesn't guarantee chA/chB sequencing, though. I'll play with this idea when I get a chance. But taken all together, it is *much* easier to sequence the data outside the TICC than within it. Something like: tail -f /dev/ttyUSB0 | tee >(grep "chA" > chA.dat) >(grep "chB" > chB.dat) should do it. (Check the syntax; I didn't actually try this out but have used the idea in the past.) John (whose hair, at least what's left of it, is more gray after having wrestled with this for the last several months) ---- On 4/14/20 1:10 PM, Bob kb8tq wrote: > Hi > > Have you tried it with the latest firmware update? > > I’ve never seen the problem here. > > Bob > >> On Apr 14, 2020, at 1:05 PM, Taka Kamiya via time-nuts <time-nuts@lists.febo.com> wrote: >> >> Bob, Tobias, et al >> >> TICC (TAPR) isn't problem free either. It has a tendency to get TimeLab confused on data from port A and port B. The data stream has identifier on them but TimeLab discards it. Then it expects A and B comes alternately. I communicated with both developers but for time being, the solution is to record the data and inspect. >> >> --------------------------------------- >> (Mr.) Taka Kamiya >> KB4EMF / ex JF2DKG >> >> >> On Tuesday, April 14, 2020, 7:48:34 AM EDT, Bob kb8tq <kb8tq@n1k.org> wrote: >> >> Hi >> >> If the phase slips are “well behaved” they can be handled. The problem >> with a dual channel setup is that they are often not well behaved. The >> period is 100 ns so a frequency drift of 1 ppb will put you in trouble in >> under 2 minutes. >> >> The only real answer is to do it properly and time tag the two outputs. >> Any other approach will get you yelling and screaming at the test set. >> Playing with two counters and not time tagging is in the “yelling and >> screaming” category as well. >> >> Get a TAPPR TICC if you really want to do a DMTD. >> >> Of course you *could* just use a single mixer. That works fine with the >> counter you already have. It will give you an A to B test just like a >> DMTD. The only limitation is the need to tune at least one of the oscillators >> in each pair. >> >> There is no requirement that you tune only one. If both are tunable, >> you could tune one to the high end of its range and the other to the low end. >> With most OCXO’s, there is plenty of tune range. >> >> Bob >> >>> On Apr 14, 2020, at 2:23 AM, Tobias Pluess <tpluess@ieee.org> wrote: >>> >>> Hey Bob >>> >>> ok now I see your point! you talk about the phase spillovers. Timelab and >>> also Stable32 can correct for them, so it shouldn't be a problem, right? >>> >>> But I agree, if you cannot correct for the spillovers it becomes even more >>> difficult. >>> >>> >>> Tobias >>> >>> On Tue., 14 Apr. 2020, 01:38 Bob kb8tq, <kb8tq@n1k.org> wrote: >>> >>>> Hi >>>> >>>> The gotcha with using a conventional counter (as opposed to a time tagger) >>>> is that you never know when things are going to “slip” past each other. >>>> When they >>>> do you get a major burp in your data. Bill’s setup is running a time >>>> tagger …. >>>> >>>> ( = It runs an internal time count, each edge gets “labeled” with a >>>> precise time >>>> stamp that is good to nanoseconds or picoseconds. A Time Interval Counter >>>> simply measures the time between edges. That sounds like the same thing, >>>> but >>>> it’s not quite ….) >>>> >>>> >>>>> On Apr 13, 2020, at 6:11 PM, Tobias Pluess <tpluess@ieee.org> wrote: >>>>> >>>>> Hi Bob >>>>> >>>>> Riley suggests to use a single TIC >>>>> >>>>> http://wriley.com/A%20Small%20DMTD%20System.pdf >>>>> >>>>> when you look at the block diagram Fig. 4, you can see that one TIC >>>> allows >>>>> to compare two oscillators. >>>>> I don't know exactly how, though :-) >>>> >>>> The gotcha with using a conventional counter (as opposed to a time tagger) >>>> is that you never know when things are going to “slip” past each other. >>>> When they >>>> do you get a major burp in your data. Bill’s setup is running a time >>>> tagger …. >>>> >>>>> >>>>> OK and I see your point on the 8663. I will try to use another reference! >>>>> I definitely didn't keep mine on for a long time. I didn't use the signal >>>>> generator for a while now, so it was unplugged for a few months. I assume >>>>> that's far from optimal for the 10811's stability. >>>> >>>> Best approach is to mount your reference off on it’s own and just power >>>> it. That way >>>> you don’t wear out all the guts of a fancy piece of gear. >>>> >>>> Bob >>>> >>>>> >>>>> >>>>> Tobias >>>>> >>>>> >>>>> >>>>> On Mon., 13 Apr. 2020, 23:53 Bob kb8tq, <kb8tq@n1k.org> wrote: >>>>> >>>>>> Hi >>>>>> >>>>>>> On Apr 13, 2020, at 5:06 PM, Tobias Pluess <tpluess@ieee.org> wrote: >>>>>>> >>>>>>> Hi Bob >>>>>>> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-) >>>>>>> >>>>>>> Maybe I have some good OpAmps for this purpose in my box. I will try >>>> it! >>>>>> of >>>>>> >>>>>> You need something that is quiet (like the OP-37) and has a pretty good >>>>>> slew >>>>>> rate. Past that, there are a lot of candidates. The TI OPA-228 family is >>>>>> one. >>>>>> >>>>>>> course I saw that my setup was not ideal as there was a bit of noise on >>>>>> the >>>>>>> signals which I guess does lead to some jitter in the trigger circuit >>>> and >>>>>>> therefore decreases my measurement noise floor. >>>>>> >>>>>> Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good >>>>>> digits. >>>>>> Net result is a measurement that’s good in the vicinity of parts in >>>> 10^-13 >>>>>> >>>>>>> >>>>>>> Can you say something about how it would be done using a TIC? >>>>>>> I don't have two identically good counters, but the HP 5335A could be >>>>>> used >>>>>>> as TIC, couldn't it. >>>>>> >>>>>> The standard way of doing the test is to run two counters / two TIC/s / >>>>>> two whatever’s. >>>>>> I know of no practical way to do it with a single 5335. >>>>>> >>>>>>> >>>>>>> And the offset source I used is not directly the HP 10811, but the HP >>>>>> 8663A >>>>>>> Signal generator internally uses a 10811 as reference source. But I >>>>>> didn't >>>>>>> wait for days for it to warm up properly. (Should I?) >>>>>> >>>>>> The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of >>>> how >>>>>> you >>>>>> use the 10811, it needs to be on for a while. How long very much depends >>>>>> on >>>>>> just how long it’s been off. Best to keep it on all the time. >>>>>> >>>>>>> >>>>>>>> Fun !!! >>>>>>> Yea, of course! :-) >>>>>>> I already implemented the ADEV, MDEV and TDEV calculations in Matlab by >>>>>>> myself. I use TimeLab to see what numbers I should expect, and then I >>>>>> want >>>>>>> to compute it all myself in Matlab because I want to see how it >>>> actually >>>>>>> works. ;-) >>>>>> >>>>>> Be careful any time you code this stuff for the first time. It’s >>>> amazingly >>>>>> easy >>>>>> ( = I’ve done it ….) to make minor errors. That’s in no way to suggest >>>> that >>>>>> you should not code it up yourself. I generally do it in Excel or in C. >>>>>> >>>>>> Bob >>>>>> >>>>>>> >>>>>>> >>>>>>> Best >>>>>>> Tobias >>>>>>> >>>>>>> >>>>>>> >>>>>>> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq <kb8tq@n1k.org> wrote: >>>>>>> >>>>>>>> Hi >>>>>>>> >>>>>>>> Ok, first the math: >>>>>>>> >>>>>>>> If your offset oscillator is 10 Hz high at 10 MHz, you have a: >>>>>>>> >>>>>>>> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD >>>>>>>> >>>>>>>> You get to add a 6 to what Time Lab shows you. >>>>>>>> >>>>>>>> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier >>>>>>>> gets you to 1x10^-10 >>>>>>>> >>>>>>>> So, what’s going on? >>>>>>>> >>>>>>>> You can’t feed the mixer outputs straight into a counter. The counter >>>>>>>> front >>>>>>>> end does not handle LF audio sine waves very well. You need to do an >>>>>>>> op-amp based limiter. A pair of OP-37’s in each leg ( or something >>>>>>>> similar) >>>>>>>> should do the trick. >>>>>>>> >>>>>>>> Second, the offset source needs to be pretty good. A 10811 tuned high >>>>>> with >>>>>>>> both the mechanical trim and the EFC is a pretty good choice to start >>>>>> out. >>>>>>>> >>>>>>>> If you only have one counter, simply ignore the second channel. You >>>> are >>>>>> now >>>>>>>> running a single mixer. It still works as a comparison between the >>>>>> offset >>>>>>>> oscillator >>>>>>>> and your DUT. >>>>>>>> >>>>>>>> If you want to do it properly as a DMTD, then you set up two counters. >>>>>> One >>>>>>>> to measure mixer A and the other to measure mixer B. Set them both up >>>>>> to >>>>>>>> measure frequency. Time tag the data files so you know which reading >>>>>>>> matches up with which. >>>>>>>> >>>>>>>> Fun !!! >>>>>>>> >>>>>>>> Bob >>>>>>>> >>>>>>>>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess <tpluess@ieee.org> wrote: >>>>>>>>> >>>>>>>>> Hi again Bob >>>>>>>>> >>>>>>>>> I tried to do some measurements with a DMTD! >>>>>>>>> In my junk box I found a little PCB from earlier experiments on that >>>>>>>> topic, >>>>>>>>> with a power splitter and two SRA-3H mixers, it was even already >>>> wired >>>>>>>> for >>>>>>>>> the DMTD configuration. So I gave it a try! >>>>>>>>> As "transfer oscillator" I used my HP 8663A signal generator, and set >>>>>> it >>>>>>>>> high in frequency by 10 Hz. To the two mixers, I connected the two >>>>>> 10MHz >>>>>>>>> signals and at the mixer outputs, I put a little lowpass filter with >>>>>>>> 100Hz >>>>>>>>> corner frequency. >>>>>>>>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I >>>>>>>> tried >>>>>>>>> to feed them directly into the HP 5335A TIC and used the TI mode to >>>>>>>> measure >>>>>>>>> the delay between the two signals. >>>>>>>>> This gives 10 readings/sec, which I try to process with TimeLab. >>>>>>>>> It does give some interesting graphs, but I don't know yet how to >>>>>>>> correctly >>>>>>>>> set up TimeLab for this kind of measurement. I.e. now, I get an ADEV >>>> in >>>>>>>> the >>>>>>>>> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that >>>> mean >>>>>> I >>>>>>>>> simply need to multiply this with 1e-7 to get the *real* ADEV at >>>> 10MHz? >>>>>>>>> this would mean that my real ADEV is in the range of 1e-11 to 1e-12, >>>>>>>> which >>>>>>>>> is indeed my target value, BUT I expect that things are not that >>>>>> simple. >>>>>>>>> (i.e. what if I didn't set the transfer oscillator high by +10Hz but >>>>>> only >>>>>>>>> by 9.9Hz for example). >>>>>>>>> Can you give some hints on that? >>>>>>>>> Of course I also did the noise floor test (i.e. I fed the 10MHz >>>> signal >>>>>>>> into >>>>>>>>> a power splitter and connected the two outputs to my DMTD with two >>>>>>>>> different lenghts of cables. This gave results starting at 1e-4 going >>>>>>>> down >>>>>>>>> to 1e-7, maybe it would have gone even lower but I measured only for >>>> a >>>>>>>>> couple of minutes.) >>>>>>>>> >>>>>>>>> Can you give some hints on that? >>>>>>>>> >>>>>>>>> Best >>>>>>>>> Tobias >>>>>>>>> HB9FSX >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> >>>>>>>>> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq <kb8tq@n1k.org> wrote: >>>>>>>>>> >>>>>>>>>>> Hi >>>>>>>>>>> >>>>>>>>>>> The quick way to do this is with a single mixer. Take something >>>> like >>>>>> an >>>>>>>>>>> old >>>>>>>>>>> 10811 and use the coarse tune to set it high in frequency by 5 to >>>> 10 >>>>>>>> Hz. >>>>>>>>>>> >>>>>>>>>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio >>>>>>>> tone. >>>>>>>>>>> That tone is the *difference* between the 10811 and your device >>>> under >>>>>>>>>>> test. >>>>>>>>>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz. >>>>>>>>>>> >>>>>>>>>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very >>>>>> small >>>>>>>>>>> shift >>>>>>>>>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the >>>>>>>> change >>>>>>>>>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X >>>>>> increase >>>>>>>> ). >>>>>>>>>>> >>>>>>>>>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no, >>>> it’s >>>>>>>> not >>>>>>>>>>> that >>>>>>>>>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1 >>>>>>>>>>> second. >>>>>>>>>>> >>>>>>>>>>> The reason its not quite that simple is that the input circuit on >>>> the >>>>>>>>>>> counter >>>>>>>>>>> really does not handle a 10 Hz audio tone as well as it handles a >>>> 10 >>>>>>>> MHz >>>>>>>>>>> RF signal. Instead of getting 9 digits a second, you probably will >>>>>> get >>>>>>>>>>> three >>>>>>>>>>> *good* digits a second and another 6 digits of noise. >>>>>>>>>>> >>>>>>>>>>> The good news is that an op amp used as a preamp ( to get you up to >>>>>>>> maybe >>>>>>>>>>> 32 V p-p rather than a volt or so) and another op amp or three as >>>>>>>>>>> limiters will >>>>>>>>>>> get you up around 6 or 7 good digits. Toss in a cap or two as a >>>> high >>>>>>>> pass >>>>>>>>>>> and low pass filter ( DC offsets can be a problem ….) and you have >>>> a >>>>>>>>>>> working >>>>>>>>>>> device that gets into the parts in 10^-13 with your 5335. >>>>>>>>>>> >>>>>>>>>>> It all can be done with point to point wiring. No need for a PCB >>>>>>>> layout. >>>>>>>>>>> Be >>>>>>>>>>> careful that the +/- 18V supplies to the op amp *both* go on and >>>> off >>>>>> at >>>>>>>>>>> the >>>>>>>>>>> same time …. >>>>>>>>>>> >>>>>>>>>>> Bob >>>>>>>>>>> >>>>>>>>>> >>>>>>>>> _______________________________________________ >>>>>>>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>>>>>>> To unsubscribe, go to >>>>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>>>>>> and follow the instructions there. >>>>>>>> >>>>>>>> >>>>>>>> _______________________________________________ >>>>>>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>>>>>> To unsubscribe, go to >>>>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>>>>> and follow the instructions there. >>>>>>>> >>>>>>> _______________________________________________ >>>>>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>>>>> To unsubscribe, go to >>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>>>> and follow the instructions there. >>>>>> >>>>>> >>>>>> _______________________________________________ >>>>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>>>> To unsubscribe, go to >>>>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>>> and follow the instructions there. >>>>>> >>>>> _______________________________________________ >>>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>>> To unsubscribe, go to >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>> and follow the instructions there. >>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>> To unsubscribe, go to >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>> and follow the instructions there. >>>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@lists.febo.com >>> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. >

Hey Bob awesome, I actually have found some OP-07 and OP-37 in my junkbox! going to build an amplifier now for my mixers. Is it a wise idea to add diodes to prevent the amplifier from clipping? For example I would have done it similar to this https://www.allaboutcircuits.com/technical-articles/an-op-amp-limiter-how-to-limit-the-amplitude-of-amplified-signals/ but I don't know whether this is a timenuts-grade circuit. Tobias On Mon., 13 Apr. 2020, 23:53 Bob kb8tq, <kb8tq@n1k.org> wrote: > Hi > > > On Apr 13, 2020, at 5:06 PM, Tobias Pluess <tpluess@ieee.org> wrote: > > > > Hi Bob > > awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-) > > > > Maybe I have some good OpAmps for this purpose in my box. I will try it! > of > > You need something that is quiet (like the OP-37) and has a pretty good > slew > rate. Past that, there are a lot of candidates. The TI OPA-228 family is > one. > > > course I saw that my setup was not ideal as there was a bit of noise on > the > > signals which I guess does lead to some jitter in the trigger circuit and > > therefore decreases my measurement noise floor. > > Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good > digits. > Net result is a measurement that’s good in the vicinity of parts in 10^-13 > > > > > Can you say something about how it would be done using a TIC? > > I don't have two identically good counters, but the HP 5335A could be > used > > as TIC, couldn't it. > > The standard way of doing the test is to run two counters / two TIC/s / > two whatever’s. > I know of no practical way to do it with a single 5335. > > > > > And the offset source I used is not directly the HP 10811, but the HP > 8663A > > Signal generator internally uses a 10811 as reference source. But I > didn't > > wait for days for it to warm up properly. (Should I?) > > The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of how > you > use the 10811, it needs to be on for a while. How long very much depends > on > just how long it’s been off. Best to keep it on all the time. > > > > >> Fun !!! > > Yea, of course! :-) > > I already implemented the ADEV, MDEV and TDEV calculations in Matlab by > > myself. I use TimeLab to see what numbers I should expect, and then I > want > > to compute it all myself in Matlab because I want to see how it actually > > works. ;-) > > Be careful any time you code this stuff for the first time. It’s amazingly > easy > ( = I’ve done it ….) to make minor errors. That’s in no way to suggest that > you should not code it up yourself. I generally do it in Excel or in C. > > Bob > > > > > > > Best > > Tobias > > > > > > > > On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq <kb8tq@n1k.org> wrote: > > > >> Hi > >> > >> Ok, first the math: > >> > >> If your offset oscillator is 10 Hz high at 10 MHz, you have a: > >> > >> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD > >> > >> You get to add a 6 to what Time Lab shows you. > >> > >> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier > >> gets you to 1x10^-10 > >> > >> So, what’s going on? > >> > >> You can’t feed the mixer outputs straight into a counter. The counter > >> front > >> end does not handle LF audio sine waves very well. You need to do an > >> op-amp based limiter. A pair of OP-37’s in each leg ( or something > >> similar) > >> should do the trick. > >> > >> Second, the offset source needs to be pretty good. A 10811 tuned high > with > >> both the mechanical trim and the EFC is a pretty good choice to start > out. > >> > >> If you only have one counter, simply ignore the second channel. You are > now > >> running a single mixer. It still works as a comparison between the > offset > >> oscillator > >> and your DUT. > >> > >> If you want to do it properly as a DMTD, then you set up two counters. > One > >> to measure mixer A and the other to measure mixer B. Set them both up > to > >> measure frequency. Time tag the data files so you know which reading > >> matches up with which. > >> > >> Fun !!! > >> > >> Bob > >> > >>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess <tpluess@ieee.org> wrote: > >>> > >>> Hi again Bob > >>> > >>> I tried to do some measurements with a DMTD! > >>> In my junk box I found a little PCB from earlier experiments on that > >> topic, > >>> with a power splitter and two SRA-3H mixers, it was even already wired > >> for > >>> the DMTD configuration. So I gave it a try! > >>> As "transfer oscillator" I used my HP 8663A signal generator, and set > it > >>> high in frequency by 10 Hz. To the two mixers, I connected the two > 10MHz > >>> signals and at the mixer outputs, I put a little lowpass filter with > >> 100Hz > >>> corner frequency. > >>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I > >> tried > >>> to feed them directly into the HP 5335A TIC and used the TI mode to > >> measure > >>> the delay between the two signals. > >>> This gives 10 readings/sec, which I try to process with TimeLab. > >>> It does give some interesting graphs, but I don't know yet how to > >> correctly > >>> set up TimeLab for this kind of measurement. I.e. now, I get an ADEV in > >> the > >>> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that mean > I > >>> simply need to multiply this with 1e-7 to get the *real* ADEV at 10MHz? > >>> this would mean that my real ADEV is in the range of 1e-11 to 1e-12, > >> which > >>> is indeed my target value, BUT I expect that things are not that > simple. > >>> (i.e. what if I didn't set the transfer oscillator high by +10Hz but > only > >>> by 9.9Hz for example). > >>> Can you give some hints on that? > >>> Of course I also did the noise floor test (i.e. I fed the 10MHz signal > >> into > >>> a power splitter and connected the two outputs to my DMTD with two > >>> different lenghts of cables. This gave results starting at 1e-4 going > >> down > >>> to 1e-7, maybe it would have gone even lower but I measured only for a > >>> couple of minutes.) > >>> > >>> Can you give some hints on that? > >>> > >>> Best > >>> Tobias > >>> HB9FSX > >>> > >>> > >>> > >>> > >>> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq <kb8tq@n1k.org> wrote: > >>>> > >>>>> Hi > >>>>> > >>>>> The quick way to do this is with a single mixer. Take something like > an > >>>>> old > >>>>> 10811 and use the coarse tune to set it high in frequency by 5 to 10 > >> Hz. > >>>>> > >>>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio > >> tone. > >>>>> That tone is the *difference* between the 10811 and your device under > >>>>> test. > >>>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz. > >>>>> > >>>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very > small > >>>>> shift > >>>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the > >> change > >>>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X > increase > >> ). > >>>>> > >>>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no, it’s > >> not > >>>>> that > >>>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1 > >>>>> second. > >>>>> > >>>>> The reason its not quite that simple is that the input circuit on the > >>>>> counter > >>>>> really does not handle a 10 Hz audio tone as well as it handles a 10 > >> MHz > >>>>> RF signal. Instead of getting 9 digits a second, you probably will > get > >>>>> three > >>>>> *good* digits a second and another 6 digits of noise. > >>>>> > >>>>> The good news is that an op amp used as a preamp ( to get you up to > >> maybe > >>>>> 32 V p-p rather than a volt or so) and another op amp or three as > >>>>> limiters will > >>>>> get you up around 6 or 7 good digits. Toss in a cap or two as a high > >> pass > >>>>> and low pass filter ( DC offsets can be a problem ….) and you have a > >>>>> working > >>>>> device that gets into the parts in 10^-13 with your 5335. > >>>>> > >>>>> It all can be done with point to point wiring. No need for a PCB > >> layout. > >>>>> Be > >>>>> careful that the +/- 18V supplies to the op amp *both* go on and off > at > >>>>> the > >>>>> same time …. > >>>>> > >>>>> Bob > >>>>> > >>>> > >>> _______________________________________________ > >>> time-nuts mailing list -- time-nuts@lists.febo.com > >>> To unsubscribe, go to > >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >>> and follow the instructions there. > >> > >> > >> _______________________________________________ > >> time-nuts mailing list -- time-nuts@lists.febo.com > >> To unsubscribe, go to > >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >> and follow the instructions there. > >> > > _______________________________________________ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. >

Hi The OP-37 is fine as long as the gain is over 5X. Under that gain level, you need to run an OP-27. The OP-07 is pretty noisy. Limiter circuits have been covered in a lot of detail. One quick read is at: http://www.ko4bb.com/getsimple/index.php?id=bruces-zero-crossing-detectors <http://www.ko4bb.com/getsimple/index.php?id=bruces-zero-crossing-detectors> That page and the others Bruce did go into a lot of detail on the how and why of this kind of limiter. There are other resources out there as well. So yes, there are circuits that work better for this than others. Bob > On Apr 16, 2020, at 3:46 PM, Tobias Pluess <tpluess@ieee.org> wrote: > > Hey Bob > > awesome, I actually have found some OP-07 and OP-37 in my junkbox! going to > build an amplifier now for my mixers. Is it a wise idea to add diodes to > prevent the amplifier from clipping? > For example I would have done it similar to this > > https://www.allaboutcircuits.com/technical-articles/an-op-amp-limiter-how-to-limit-the-amplitude-of-amplified-signals/ > > but I don't know whether this is a timenuts-grade circuit. > > > Tobias > > > On Mon., 13 Apr. 2020, 23:53 Bob kb8tq, <kb8tq@n1k.org> wrote: > >> Hi >> >>> On Apr 13, 2020, at 5:06 PM, Tobias Pluess <tpluess@ieee.org> wrote: >>> >>> Hi Bob >>> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-) >>> >>> Maybe I have some good OpAmps for this purpose in my box. I will try it! >> of >> >> You need something that is quiet (like the OP-37) and has a pretty good >> slew >> rate. Past that, there are a lot of candidates. The TI OPA-228 family is >> one. >> >>> course I saw that my setup was not ideal as there was a bit of noise on >> the >>> signals which I guess does lead to some jitter in the trigger circuit and >>> therefore decreases my measurement noise floor. >> >> Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good >> digits. >> Net result is a measurement that’s good in the vicinity of parts in 10^-13 >> >>> >>> Can you say something about how it would be done using a TIC? >>> I don't have two identically good counters, but the HP 5335A could be >> used >>> as TIC, couldn't it. >> >> The standard way of doing the test is to run two counters / two TIC/s / >> two whatever’s. >> I know of no practical way to do it with a single 5335. >> >>> >>> And the offset source I used is not directly the HP 10811, but the HP >> 8663A >>> Signal generator internally uses a 10811 as reference source. But I >> didn't >>> wait for days for it to warm up properly. (Should I?) >> >> The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of how >> you >> use the 10811, it needs to be on for a while. How long very much depends >> on >> just how long it’s been off. Best to keep it on all the time. >> >>> >>>> Fun !!! >>> Yea, of course! :-) >>> I already implemented the ADEV, MDEV and TDEV calculations in Matlab by >>> myself. I use TimeLab to see what numbers I should expect, and then I >> want >>> to compute it all myself in Matlab because I want to see how it actually >>> works. ;-) >> >> Be careful any time you code this stuff for the first time. It’s amazingly >> easy >> ( = I’ve done it ….) to make minor errors. That’s in no way to suggest that >> you should not code it up yourself. I generally do it in Excel or in C. >> >> Bob >> >>> >>> >>> Best >>> Tobias >>> >>> >>> >>> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq <kb8tq@n1k.org> wrote: >>> >>>> Hi >>>> >>>> Ok, first the math: >>>> >>>> If your offset oscillator is 10 Hz high at 10 MHz, you have a: >>>> >>>> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD >>>> >>>> You get to add a 6 to what Time Lab shows you. >>>> >>>> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier >>>> gets you to 1x10^-10 >>>> >>>> So, what’s going on? >>>> >>>> You can’t feed the mixer outputs straight into a counter. The counter >>>> front >>>> end does not handle LF audio sine waves very well. You need to do an >>>> op-amp based limiter. A pair of OP-37’s in each leg ( or something >>>> similar) >>>> should do the trick. >>>> >>>> Second, the offset source needs to be pretty good. A 10811 tuned high >> with >>>> both the mechanical trim and the EFC is a pretty good choice to start >> out. >>>> >>>> If you only have one counter, simply ignore the second channel. You are >> now >>>> running a single mixer. It still works as a comparison between the >> offset >>>> oscillator >>>> and your DUT. >>>> >>>> If you want to do it properly as a DMTD, then you set up two counters. >> One >>>> to measure mixer A and the other to measure mixer B. Set them both up >> to >>>> measure frequency. Time tag the data files so you know which reading >>>> matches up with which. >>>> >>>> Fun !!! >>>> >>>> Bob >>>> >>>>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess <tpluess@ieee.org> wrote: >>>>> >>>>> Hi again Bob >>>>> >>>>> I tried to do some measurements with a DMTD! >>>>> In my junk box I found a little PCB from earlier experiments on that >>>> topic, >>>>> with a power splitter and two SRA-3H mixers, it was even already wired >>>> for >>>>> the DMTD configuration. So I gave it a try! >>>>> As "transfer oscillator" I used my HP 8663A signal generator, and set >> it >>>>> high in frequency by 10 Hz. To the two mixers, I connected the two >> 10MHz >>>>> signals and at the mixer outputs, I put a little lowpass filter with >>>> 100Hz >>>>> corner frequency. >>>>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I >>>> tried >>>>> to feed them directly into the HP 5335A TIC and used the TI mode to >>>> measure >>>>> the delay between the two signals. >>>>> This gives 10 readings/sec, which I try to process with TimeLab. >>>>> It does give some interesting graphs, but I don't know yet how to >>>> correctly >>>>> set up TimeLab for this kind of measurement. I.e. now, I get an ADEV in >>>> the >>>>> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that mean >> I >>>>> simply need to multiply this with 1e-7 to get the *real* ADEV at 10MHz? >>>>> this would mean that my real ADEV is in the range of 1e-11 to 1e-12, >>>> which >>>>> is indeed my target value, BUT I expect that things are not that >> simple. >>>>> (i.e. what if I didn't set the transfer oscillator high by +10Hz but >> only >>>>> by 9.9Hz for example). >>>>> Can you give some hints on that? >>>>> Of course I also did the noise floor test (i.e. I fed the 10MHz signal >>>> into >>>>> a power splitter and connected the two outputs to my DMTD with two >>>>> different lenghts of cables. This gave results starting at 1e-4 going >>>> down >>>>> to 1e-7, maybe it would have gone even lower but I measured only for a >>>>> couple of minutes.) >>>>> >>>>> Can you give some hints on that? >>>>> >>>>> Best >>>>> Tobias >>>>> HB9FSX >>>>> >>>>> >>>>> >>>>> >>>>> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq <kb8tq@n1k.org> wrote: >>>>>> >>>>>>> Hi >>>>>>> >>>>>>> The quick way to do this is with a single mixer. Take something like >> an >>>>>>> old >>>>>>> 10811 and use the coarse tune to set it high in frequency by 5 to 10 >>>> Hz. >>>>>>> >>>>>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio >>>> tone. >>>>>>> That tone is the *difference* between the 10811 and your device under >>>>>>> test. >>>>>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz. >>>>>>> >>>>>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very >> small >>>>>>> shift >>>>>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the >>>> change >>>>>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X >> increase >>>> ). >>>>>>> >>>>>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no, it’s >>>> not >>>>>>> that >>>>>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1 >>>>>>> second. >>>>>>> >>>>>>> The reason its not quite that simple is that the input circuit on the >>>>>>> counter >>>>>>> really does not handle a 10 Hz audio tone as well as it handles a 10 >>>> MHz >>>>>>> RF signal. Instead of getting 9 digits a second, you probably will >> get >>>>>>> three >>>>>>> *good* digits a second and another 6 digits of noise. >>>>>>> >>>>>>> The good news is that an op amp used as a preamp ( to get you up to >>>> maybe >>>>>>> 32 V p-p rather than a volt or so) and another op amp or three as >>>>>>> limiters will >>>>>>> get you up around 6 or 7 good digits. Toss in a cap or two as a high >>>> pass >>>>>>> and low pass filter ( DC offsets can be a problem ….) and you have a >>>>>>> working >>>>>>> device that gets into the parts in 10^-13 with your 5335. >>>>>>> >>>>>>> It all can be done with point to point wiring. No need for a PCB >>>> layout. >>>>>>> Be >>>>>>> careful that the +/- 18V supplies to the op amp *both* go on and off >> at >>>>>>> the >>>>>>> same time …. >>>>>>> >>>>>>> Bob >>>>>>> >>>>>> >>>>> _______________________________________________ >>>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>>> To unsubscribe, go to >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>>> and follow the instructions there. >>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- time-nuts@lists.febo.com >>>> To unsubscribe, go to >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>>> and follow the instructions there. >>>> >>> _______________________________________________ >>> time-nuts mailing list -- time-nuts@lists.febo.com >>> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >>> and follow the instructions there. >> >> >> _______________________________________________ >> time-nuts mailing list -- time-nuts@lists.febo.com >> To unsubscribe, go to >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com >> and follow the instructions there. >> > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there.

An OP37 may not function well as a diode clamped limiter since the loop gain is <5 during limiting. A unity gain stable opamp would likely be better. Bruce > On 17 April 2020 at 09:26 Bob kb8tq <kb8tq@n1k.org> wrote: > > > Hi > > The OP-37 is fine as long as the gain is over 5X. Under that gain level, you > need to run an OP-27. The OP-07 is pretty noisy. > > Limiter circuits have been covered in a lot of detail. One quick read is at: > > http://www.ko4bb.com/getsimple/index.php?id=bruces-zero-crossing-detectors <http://www.ko4bb.com/getsimple/index.php?id=bruces-zero-crossing-detectors> > > That page and the others Bruce did go into a lot of detail on the how and > why of this kind of limiter. There are other resources out there as well. > > So yes, there are circuits that work better for this than others. > > Bob > > > On Apr 16, 2020, at 3:46 PM, Tobias Pluess <tpluess@ieee.org> wrote: > > > > Hey Bob > > > > awesome, I actually have found some OP-07 and OP-37 in my junkbox! going to > > build an amplifier now for my mixers. Is it a wise idea to add diodes to > > prevent the amplifier from clipping? > > For example I would have done it similar to this > > > > https://www.allaboutcircuits.com/technical-articles/an-op-amp-limiter-how-to-limit-the-amplitude-of-amplified-signals/ > > > > but I don't know whether this is a timenuts-grade circuit. > > > > > > Tobias > > > > > > On Mon., 13 Apr. 2020, 23:53 Bob kb8tq, <kb8tq@n1k.org> wrote: > > > >> Hi > >> > >>> On Apr 13, 2020, at 5:06 PM, Tobias Pluess <tpluess@ieee.org> wrote: > >>> > >>> Hi Bob > >>> awesome, thanks! of course it is 1e6, not 1e7, I got a mistake :-) > >>> > >>> Maybe I have some good OpAmps for this purpose in my box. I will try it! > >> of > >> > >> You need something that is quiet (like the OP-37) and has a pretty good > >> slew > >> rate. Past that, there are a lot of candidates. The TI OPA-228 family is > >> one. > >> > >>> course I saw that my setup was not ideal as there was a bit of noise on > >> the > >>> signals which I guess does lead to some jitter in the trigger circuit and > >>> therefore decreases my measurement noise floor. > >> > >> Typically a good limiter takes you from 3 or 4 digits up to 6 or 7 good > >> digits. > >> Net result is a measurement that’s good in the vicinity of parts in 10^-13 > >> > >>> > >>> Can you say something about how it would be done using a TIC? > >>> I don't have two identically good counters, but the HP 5335A could be > >> used > >>> as TIC, couldn't it. > >> > >> The standard way of doing the test is to run two counters / two TIC/s / > >> two whatever’s. > >> I know of no practical way to do it with a single 5335. > >> > >>> > >>> And the offset source I used is not directly the HP 10811, but the HP > >> 8663A > >>> Signal generator internally uses a 10811 as reference source. But I > >> didn't > >>> wait for days for it to warm up properly. (Should I?) > >> > >> The 8663 synthesizer adds a *lot* of crud to the 10811. Regardless of how > >> you > >> use the 10811, it needs to be on for a while. How long very much depends > >> on > >> just how long it’s been off. Best to keep it on all the time. > >> > >>> > >>>> Fun !!! > >>> Yea, of course! :-) > >>> I already implemented the ADEV, MDEV and TDEV calculations in Matlab by > >>> myself. I use TimeLab to see what numbers I should expect, and then I > >> want > >>> to compute it all myself in Matlab because I want to see how it actually > >>> works. ;-) > >> > >> Be careful any time you code this stuff for the first time. It’s amazingly > >> easy > >> ( = I’ve done it ….) to make minor errors. That’s in no way to suggest that > >> you should not code it up yourself. I generally do it in Excel or in C. > >> > >> Bob > >> > >>> > >>> > >>> Best > >>> Tobias > >>> > >>> > >>> > >>> On Mon, Apr 13, 2020 at 10:50 PM Bob kb8tq <kb8tq@n1k.org> wrote: > >>> > >>>> Hi > >>>> > >>>> Ok, first the math: > >>>> > >>>> If your offset oscillator is 10 Hz high at 10 MHz, you have a: > >>>> > >>>> 10,000,000 / 10 = 1,000,000 : 1 multiplier in front of the DMTD > >>>> > >>>> You get to add a 6 to what Time Lab shows you. > >>>> > >>>> If you are getting an ADEV at 1 second of 1x10^-4 then that multiplier > >>>> gets you to 1x10^-10 > >>>> > >>>> So, what’s going on? > >>>> > >>>> You can’t feed the mixer outputs straight into a counter. The counter > >>>> front > >>>> end does not handle LF audio sine waves very well. You need to do an > >>>> op-amp based limiter. A pair of OP-37’s in each leg ( or something > >>>> similar) > >>>> should do the trick. > >>>> > >>>> Second, the offset source needs to be pretty good. A 10811 tuned high > >> with > >>>> both the mechanical trim and the EFC is a pretty good choice to start > >> out. > >>>> > >>>> If you only have one counter, simply ignore the second channel. You are > >> now > >>>> running a single mixer. It still works as a comparison between the > >> offset > >>>> oscillator > >>>> and your DUT. > >>>> > >>>> If you want to do it properly as a DMTD, then you set up two counters. > >> One > >>>> to measure mixer A and the other to measure mixer B. Set them both up > >> to > >>>> measure frequency. Time tag the data files so you know which reading > >>>> matches up with which. > >>>> > >>>> Fun !!! > >>>> > >>>> Bob > >>>> > >>>>> On Apr 13, 2020, at 3:18 PM, Tobias Pluess <tpluess@ieee.org> wrote: > >>>>> > >>>>> Hi again Bob > >>>>> > >>>>> I tried to do some measurements with a DMTD! > >>>>> In my junk box I found a little PCB from earlier experiments on that > >>>> topic, > >>>>> with a power splitter and two SRA-3H mixers, it was even already wired > >>>> for > >>>>> the DMTD configuration. So I gave it a try! > >>>>> As "transfer oscillator" I used my HP 8663A signal generator, and set > >> it > >>>>> high in frequency by 10 Hz. To the two mixers, I connected the two > >> 10MHz > >>>>> signals and at the mixer outputs, I put a little lowpass filter with > >>>> 100Hz > >>>>> corner frequency. > >>>>> The output signals from the two SRA-3 mixers are almost 0.5Vpp, so I > >>>> tried > >>>>> to feed them directly into the HP 5335A TIC and used the TI mode to > >>>> measure > >>>>> the delay between the two signals. > >>>>> This gives 10 readings/sec, which I try to process with TimeLab. > >>>>> It does give some interesting graphs, but I don't know yet how to > >>>> correctly > >>>>> set up TimeLab for this kind of measurement. I.e. now, I get an ADEV in > >>>> the > >>>>> order of 1e-4 (at tau=1sec) to 1e-5 (at tau=500sec). So does that mean > >> I > >>>>> simply need to multiply this with 1e-7 to get the *real* ADEV at 10MHz? > >>>>> this would mean that my real ADEV is in the range of 1e-11 to 1e-12, > >>>> which > >>>>> is indeed my target value, BUT I expect that things are not that > >> simple. > >>>>> (i.e. what if I didn't set the transfer oscillator high by +10Hz but > >> only > >>>>> by 9.9Hz for example). > >>>>> Can you give some hints on that? > >>>>> Of course I also did the noise floor test (i.e. I fed the 10MHz signal > >>>> into > >>>>> a power splitter and connected the two outputs to my DMTD with two > >>>>> different lenghts of cables. This gave results starting at 1e-4 going > >>>> down > >>>>> to 1e-7, maybe it would have gone even lower but I measured only for a > >>>>> couple of minutes.) > >>>>> > >>>>> Can you give some hints on that? > >>>>> > >>>>> Best > >>>>> Tobias > >>>>> HB9FSX > >>>>> > >>>>> > >>>>> > >>>>> > >>>>> On Fri, Apr 3, 2020 at 1:45 PM Bob kb8tq <kb8tq@n1k.org> wrote: > >>>>>> > >>>>>>> Hi > >>>>>>> > >>>>>>> The quick way to do this is with a single mixer. Take something like > >> an > >>>>>>> old > >>>>>>> 10811 and use the coarse tune to set it high in frequency by 5 to 10 > >>>> Hz. > >>>>>>> > >>>>>>> Then feed it into an RPD-1 mixer and pull out the 5 to 10 Hz audio > >>>> tone. > >>>>>>> That tone is the *difference* between the 10811 and your device under > >>>>>>> test. > >>>>>>> If the DUT moves 1 Hz, the audio tone changes by 1 Hz. > >>>>>>> > >>>>>>> If you measured the 10 MHz on the DUT, that 1 Hz would be a very > >> small > >>>>>>> shift > >>>>>>> ( 0.1 ppm ). At 10 Hz it’s a 10% change. You have “amplified” the > >>>> change > >>>>>>> in frequency by the ratio of 10 MHz to 10 Hz ( so a million X > >> increase > >>>> ). > >>>>>>> > >>>>>>> *IF* you could tack that on to the ADEV plot of your 5335 ( no, it’s > >>>> not > >>>>>>> that > >>>>>>> simple) your 7x10^-10 at 1 second would become more 7x10^-16 at 1 > >>>>>>> second. > >>>>>>> > >>>>>>> The reason its not quite that simple is that the input circuit on the > >>>>>>> counter > >>>>>>> really does not handle a 10 Hz audio tone as well as it handles a 10 > >>>> MHz > >>>>>>> RF signal. Instead of getting 9 digits a second, you probably will > >> get > >>>>>>> three > >>>>>>> *good* digits a second and another 6 digits of noise. > >>>>>>> > >>>>>>> The good news is that an op amp used as a preamp ( to get you up to > >>>> maybe > >>>>>>> 32 V p-p rather than a volt or so) and another op amp or three as > >>>>>>> limiters will > >>>>>>> get you up around 6 or 7 good digits. Toss in a cap or two as a high > >>>> pass > >>>>>>> and low pass filter ( DC offsets can be a problem ….) and you have a > >>>>>>> working > >>>>>>> device that gets into the parts in 10^-13 with your 5335. > >>>>>>> > >>>>>>> It all can be done with point to point wiring. No need for a PCB > >>>> layout. > >>>>>>> Be > >>>>>>> careful that the +/- 18V supplies to the op amp *both* go on and off > >> at > >>>>>>> the > >>>>>>> same time …. > >>>>>>> > >>>>>>> Bob > >>>>>>> > >>>>>> > >>>>> _______________________________________________ > >>>>> time-nuts mailing list -- time-nuts@lists.febo.com > >>>>> To unsubscribe, go to > >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >>>>> and follow the instructions there. > >>>> > >>>> > >>>> _______________________________________________ > >>>> time-nuts mailing list -- time-nuts@lists.febo.com > >>>> To unsubscribe, go to > >>>> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >>>> and follow the instructions there. > >>>> > >>> _______________________________________________ > >>> time-nuts mailing list -- time-nuts@lists.febo.com > >>> To unsubscribe, go to > >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >>> and follow the instructions there. > >> > >> > >> _______________________________________________ > >> time-nuts mailing list -- time-nuts@lists.febo.com > >> To unsubscribe, go to > >> http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > >> and follow the instructions there. > >> > > _______________________________________________ > > time-nuts mailing list -- time-nuts@lists.febo.com > > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > > and follow the instructions there. > > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there.

An old digital clock I was planning to toss has some parts that might be of interest to someone restoring old hp counters. 4 Nixie tube driver IC’s, hp 1820-0092 6 Nixie tubes, Burroughs B-5750S 4 hp decade counter IC’s, no part number but works with 1820-0092. The parts are on 0.1 inch center proto board. Leads go thru holes and are soldered point to point on the back. It shouldn’t be hard to pull the parts. Clock is about 50 years old and parts have about 25 years operation. Contact me off list if you’re interested.

Dear Colleagues I have made some tests with my self-made GPSDO which we discussed on this very list. I was allowed to install it at my workplace and put the antenna on the roof, with almost 360° free sky view. (I will have to compare different oscillators anyways, so I could install mine as well. I have also ordered some Rb standards which I will use for further comparisons.) OK what I did so far is just log the output of my GPSDO to a text file. My software which runs on the GPSDO outputs every second the 1PPS phase error, the OCXO current, board temperature, DAC value, #of satellites tracked and the position accuracy. The phase error is measured with a builtin TIC and is the time difference between the 1PPS signal from the GPS module vs. the 1PPS signal derived from my OCXO and is the input to my control loop which then forms a PLL. I thought, maybe the measurements are of interest for some members of this group, this is why I post this message and uploaded some of my measurement data here: https://hb9fsx.ch/files/gpsdo/measurement/ on the jpg images, one can see my antenna location. It is not optimal, I know, but far better than at home on my window still! (unfortunately, I could not use this very nice Trimble antenna seen on one of the pictures.) In the Lady Heather screenshot, one can see, for comparison, the satellites tracked by my GPSDO compared to the ones tracked by a commercial GPSDO. Nice to see that the C/N0 values and the SV IDs seem to be the same, from this I conclude that my PCB layout of the RF part seems to be acceptable (otherwise the signal reception would be degraded I assume). So far, my GPSDO runs for 210 hours and continuously logs its data. On the picture `gpsdo_0_210.png` one can see the data from the full run. The x-axis is in hours (obviously). Also note that I cut off the first couple of minutes of the logged data (just because the control loop needs to settle there and therefore the phase error is not so nice and would disrupt the y-axis). Apparently, the phase error never becomes larger than +/-20ns. On the picture `gpsdo_180_210.png` one can see the last 30 hours of my measured data. During this time, the DAC value need to change only by 9 counts. I think the DAC value has a slight trend to go lower and lower, this is perhaps because my OCXO was new and is still a bit aging. Phase error stays within +/-15ns during the whole time! On the image `gpsdo_pos_to_timing.png` one can see when the GPS receiver automatically switches from positioning to timing mode. At the beginning, I started a self-survey where I specified a desired position accuracy of 200mm. (What would be a sensible value for the desired position accuracy?) On the lowest chart, I added the position standard deviation reported by the GPS module. We can clearly see, at about time 9h, that the 200mm limit is reached and the module switches from positioning mode to timing mode. At this time, we can also see how the jitter behaviour of the phase error changes slightly. I assume this is because the timing mode offers a better jitter performance of the 1PPS output and therefore my phase error in the end also becomes less noisy. The last plot I have so far is `gpsdo_switch_filters.png` which is the data recorded during the initial startup phase. In my GPSDO control software, I use a PI controller where I automatically change the P and I coefficients depending on how stable the phase error was previously. We can see that up to approx. 0.35h, the DAC output follows the phase error rather quickly. For startup, I optimised my control loop such that it has a time constant of approx. 10sec, which allows the phase error to stabilise quickly. At 0.35h, the phase error was within certain limits for long enough time such that the control software decides to switch the P and I coefficients such that the control loop's time constant becomes approx. 100sec. From there on, we can see how the DAC output immediately becomes more quiet and stable. Later, the time constant is again increased to 1000sec. (I don't know whether this is good for the OCXO I have - but somewhere I read that the Oscilloquartz STAR4 uses 200sec as default but it could be much more, this is why I increased it on my unit to 400sec.) As I still don't have a proper DMTD system or anything similar which allows me to `quickly` estimate the stability of my device, I made some experiments and imported my logged data int Timelab. This can be seen in the picture `timelab_estimated_from_dac.png`. The blue curve results when I analyse the phase error. As expected, since this is essentially the performance of the 1PPS signal, the curve goes lower and lower. (I imported this data as "phase difference" and scaled it with 1e-9). The pink curve results when I let Timelab analyse the DAC values. This idea is actually from a colleague on this list. It assumes that the OCXO is perfectly stable and the only instability comes from the DAC being disturbed by the 1PPS noise. To analyse this, I imported the data as "Frequency Difference" and scaled it appropriately (scaling factor is 7.6e-12 as I have approx. 5 to 6Hz tuning range of the OCXO per 16 Bits). I am not sure how accurate this estimation will be, but if it is only close to the reality then it appears that my GPSDO has a stability in the range 1e-12. According to John's comparisons here: http://www.ke5fx.com/gpscomp.htm this would mean it is slightly better than a BG7TBL and quite a bit worse than a Tbolt with 10811A oscillator. Comments welcome. I hope I get my two Rb standards soon and can then do some DMTD tests. Tobias HB9FSX

On Mittwoch, 12. August 2020 13:23:57 CEST Tobias Pluess wrote: > On the picture `gpsdo_180_210.png` one can see the last 30 hours of my > measured data. During this time, the DAC value need to change only by 9 > counts. I think the DAC value has a slight trend to go lower and lower, > this is perhaps because my OCXO was new and is still a bit aging. Phase > error stays within +/-15ns during the whole time! TimeLab can tell you the linear drift from the imported data. > As I still don't have a proper DMTD system or anything similar which allows > me to `quickly` estimate the stability of my device, I made some > experiments and imported my logged data int Timelab. This can be seen in > the picture `timelab_estimated_from_dac.png`. The blue curve results when I > analyse the phase error. As expected, since this is essentially the > performance of the 1PPS signal, the curve goes lower and lower. (I imported > this data as "phase difference" and scaled it with 1e-9). > The pink curve results when I let Timelab analyse the DAC values. This idea > is actually from a colleague on this list. It assumes that the OCXO is > perfectly stable and the only instability comes from the DAC being > disturbed by the 1PPS noise. To analyse this, I imported the data as > "Frequency Difference" and scaled it appropriately (scaling factor is > 7.6e-12 as I have approx. 5 to 6Hz tuning range of the OCXO per 16 Bits). I > am not sure how accurate this estimation will be, but if it is only close > to the reality then it appears that my GPSDO has a stability in the range > 1e-12. According to John's comparisons here: > > http://www.ke5fx.com/gpscomp.htm > > this would mean it is slightly better than a BG7TBL and quite a bit worse > than a Tbolt with 10811A oscillator. The DAC analysis tells you mainly how much "instability" the regulation causes for a given tau. The GPSDO output can not be better than this value. Typically, it's worse than the DAC ADEV. I've been doing some simulations with TvBs GPSDO simulator a while ago (might have posted some graphs here, cannot quite remember), the DAC ADEV (or MDEV) starts to influence the OCXO performance when they become close. > Comments welcome. I hope I get my two Rb standards soon and can then do > some DMTD tests. Looking forward to seeing some actual measurements! > > > Tobias > HB9FSX > _______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow > the instructions there.