Re: [time-nuts] FTS-4040/A - Looking for voltage on switching power supply
I will believe if its the supply going to the inverter, the inverter is flexible. Most offer a fairly wide range on the input. So 24-28 is most likely very reasonable. But continue to research and just maybe you will find better detail. Pictures may also be helpful. ?? Is it a linear supply feeding the inverter?? That would make sense. Regards Paul. On Sun, Mar 17, 2019 at 5:19 PM Taka Kamiya wrote: > Now it is certain the failure is power supply. I fed 26V into DC port and > everything is working as before. I'd rather replace this faulty supply. > Question is, 24V? 28V? 30V? or 28.45V? This power supply appears to be > a custom unit. Still looking for spec on power supply. > > At least it's not the cesium tube phew! > > --- > (Mr.) Taka Kamiya > I'm stuck in a wormhole Hello, worms! > > > On Sunday, March 17, 2019, 3:59:57 PM EDT, paul swed > wrote: > > > Taka > No familiarity with 4040 and I don't have schematics. > But thats not unusual for a lot of time-nuts equipment. > But happy to give a remote hand. (Travelling this coming week so slow > responses) > Others may have more useful details like a schematic. > Regards > Paul > WB8TSL > > > On Sun, Mar 17, 2019 at 3:02 PM Taka Kamiya via time-nuts < > time-nuts@lists.febo.com> wrote: > > I have an FTS-4040/A Cesium Oscillator from Datum. It was working last > night and dead today. A/C available LED is lit but nothing else. Checking > power supply, I read 8.9V. (large switching supply on back panel) Rather > odd voltage I thought. Checked some ICs on a board. It's not getting > power. > > Does anyone have this unit or know what this switching supply is supposed > to output? It is a single voltage supply. > > --- > (Mr.) Taka Kamiya > I'm stuck in a wormhole Hello, worms! > ___ > 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.
Re: [time-nuts] Distribution amplifier for 10MHz and 1 pps
Hi CMOS is good. The faster the better. Go to your favorite vendor and find whatever is “king” this month and that’s what you go with. HC has been around a *long* time and is about as slow as it gets in terms of 5V CMOS ( yes, 4000 series is slower still …). Faster means less delay in the gate (so lower variation in delay). It also turns out that faster means lower phase noise so lower jitter. Buffers are better than inverters, simply because they have higher output drive capability. One “favorite” are the x125 and x126 tri-state buffers. NC7SZ125 and NC7SZ126 are two examples. If you want to drive 50 ohms, you likely will need to parallel gates in order to handle the current. There is an ongoing debate about source termination vs load termination vs “both termination” vs “don’t bother”. I would suggest that terminating one end or the other is a … errr …. really good idea. Lots more information in the archives. Bob > On Mar 17, 2019, at 6:39 PM, Taka Kamiya via time-nuts > wrote: > > I'm very curious, too. Especially when I *just* built one using 74HC04N. > > --- > (Mr.) Taka Kamiya > I'm stuck in a wormhole Hello, worms! > >On Sunday, March 17, 2019, 4:01:26 PM EDT, Hal Murray > wrote: > > >> For 1PPs the main goal is jitter and the selection of the ICs is very tricky > > Could you please say more? Do you mean logic family selection, or chip > selection within a family? > > Most modern digital chips are CMOS with an input threshold of VCC/2. I'd > expect power supply noise to be important and families with faster switching > times probably make more noise. > > > -- > These are my opinions. I hate spam. > > > > > ___ > 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.
Re: [time-nuts] FTS-4040/A - Looking for voltage on switching power supply
Now it is certain the failure is power supply. I fed 26V into DC port and everything is working as before. I'd rather replace this faulty supply. Question is, 24V? 28V? 30V? or 28.45V? This power supply appears to be a custom unit. Still looking for spec on power supply. At least it's not the cesium tube phew! --- (Mr.) Taka Kamiya I'm stuck in a wormhole Hello, worms! On Sunday, March 17, 2019, 3:59:57 PM EDT, paul swed wrote: TakaNo familiarity with 4040 and I don't have schematics.But thats not unusual for a lot of time-nuts equipment.But happy to give a remote hand. (Travelling this coming week so slow responses)Others may have more useful details like a schematic.RegardsPaulWB8TSL On Sun, Mar 17, 2019 at 3:02 PM Taka Kamiya via time-nuts wrote: I have an FTS-4040/A Cesium Oscillator from Datum. It was working last night and dead today. A/C available LED is lit but nothing else. Checking power supply, I read 8.9V. (large switching supply on back panel) Rather odd voltage I thought. Checked some ICs on a board. It's not getting power. Does anyone have this unit or know what this switching supply is supposed to output? It is a single voltage supply. --- (Mr.) Taka Kamiya I'm stuck in a wormhole Hello, worms! ___ 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.
Re: [time-nuts] Distribution amplifier for 10MHz and 1 pps
Hi Yup, pretty much the same questions each time. I’ve given up recommending specific IC’s since the DIY approach does not seem to be what people are after. That’s not a problem, I do a *lot* of stuff on a “what’s on eBay?” basis. Bob > On Mar 17, 2019, at 4:56 PM, djl wrote: > > Gosh. this topic comes up at least once every 6 months. A diligent search of > the time-nuts database would turn up amazing things. . . > > > On 2019-03-17 13:24, Hal Murray wrote: >>> For 1PPs the main goal is jitter and the selection of the ICs is very tricky >> Could you please say more? Do you mean logic family selection, or chip >> selection within a family? >> Most modern digital chips are CMOS with an input threshold of VCC/2. I'd >> expect power supply noise to be important and families with faster switching >> times probably make more noise. > > -- > Dr. Don Latham AJ7LL > PO Box 404, Frenchtown, MT, 59834 > VOX: 406-626-4304 > > > ___ > 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.
Re: [time-nuts] Distribution amplifier for 10MHz and 1 pps
I'm very curious, too. Especially when I *just* built one using 74HC04N. --- (Mr.) Taka Kamiya I'm stuck in a wormhole Hello, worms! On Sunday, March 17, 2019, 4:01:26 PM EDT, Hal Murray wrote: > For 1PPs the main goal is jitter and the selection of the ICs is very tricky Could you please say more? Do you mean logic family selection, or chip selection within a family? Most modern digital chips are CMOS with an input threshold of VCC/2. I'd expect power supply noise to be important and families with faster switching times probably make more noise. -- These are my opinions. I hate spam. ___ 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.
Re: [time-nuts] Frequency Ensemble
Hi TAPPR needs that order for 25 TICC’s …… :) There are indeed many ways to do it and each has it’s advantages and disadvantages. With a DMTD sort of system, you can’t grab “off the shelf” hardware to get things up and running quickly. Also the isolation / ground loop / spur problem is very likely to get you on a DMTD like system with 20 to 30 devices on the same “party line”. No ideal answer, just a lot of tradeoff’s. Bob > On Mar 17, 2019, at 4:48 PM, Attila Kinali wrote: > > On Sun, 17 Mar 2019 10:58:49 -0400 > Bob kb8tq wrote: > >> The first thing you need (after all the standards) is a way to do precision >> comparisons of all your devices. There are an infinite number of ways to do >> this. Let’s say you buy 26 TICC’s to do the job ( TAPPR needs 25 ordered to >> get the next batch going so that would solve two problems at once :) ). A >> PPS from a single source with good short term stability (maybe an OCXO) goes >> into one side of all of them. A pps from a DUT goes in the other side (yes >> there are other ways …TAPPR needs that order ….). >> You then have 26 devices each reporting how a single standard compares to >> the “main OCXO”. > > > I would use here a variant of DMTD: Instead of comparing pairs > of standards, have one offset frequency generator feed multiple > mixers, one for each standard. This way, the standards can be > compared to eachother more easily. Downside of this is, that > the precision of this comparison depends on the stability of > the distribution of the offset frequency signal. Though, under > the assumption that ground loops can be kept in check, this > should be easier to ensure than having pair wise comparisons > not drifting away too much. When using TICCs, with their high > measurement rate, I would also go for an offset frequency in > the order of 1kHz instead of the customary 1-10Hz. This will > help getting away from the flicker noise region and also give > a much higher slope of the signal to work with, reducing the > white noise of the measurement. Additonally, this should > also give higher precision at tau = 1s, as the system is now > averaging down from 1ms instead of 100ms (when using 10Hz), > which could potentially give a boost of a factor of sqrt(100ms/1ms) = 10. > > Attila Kinali > > -- > The bad part of Zurich is where the degenerates >throw DARK chocolate at you. > > ___ > 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.
Re: [time-nuts] Distribution amplifier for 10MHz and 1 pps
Gosh. this topic comes up at least once every 6 months. A diligent search of the time-nuts database would turn up amazing things. . . On 2019-03-17 13:24, Hal Murray wrote: For 1PPs the main goal is jitter and the selection of the ICs is very tricky Could you please say more? Do you mean logic family selection, or chip selection within a family? Most modern digital chips are CMOS with an input threshold of VCC/2. I'd expect power supply noise to be important and families with faster switching times probably make more noise. -- Dr. Don Latham AJ7LL PO Box 404, Frenchtown, MT, 59834 VOX: 406-626-4304 ___ 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.
Re: [time-nuts] Frequency Ensemble
On Sun, 17 Mar 2019 10:58:49 -0400 Bob kb8tq wrote: > The first thing you need (after all the standards) is a way to do precision > comparisons of all your devices. There are an infinite number of ways to do > this. Let’s say you buy 26 TICC’s to do the job ( TAPPR needs 25 ordered to > get the next batch going so that would solve two problems at once :) ). A > PPS from a single source with good short term stability (maybe an OCXO) goes > into one side of all of them. A pps from a DUT goes in the other side (yes > there are other ways …TAPPR needs that order ….). > You then have 26 devices each reporting how a single standard compares to > the “main OCXO”. I would use here a variant of DMTD: Instead of comparing pairs of standards, have one offset frequency generator feed multiple mixers, one for each standard. This way, the standards can be compared to eachother more easily. Downside of this is, that the precision of this comparison depends on the stability of the distribution of the offset frequency signal. Though, under the assumption that ground loops can be kept in check, this should be easier to ensure than having pair wise comparisons not drifting away too much. When using TICCs, with their high measurement rate, I would also go for an offset frequency in the order of 1kHz instead of the customary 1-10Hz. This will help getting away from the flicker noise region and also give a much higher slope of the signal to work with, reducing the white noise of the measurement. Additonally, this should also give higher precision at tau = 1s, as the system is now averaging down from 1ms instead of 100ms (when using 10Hz), which could potentially give a boost of a factor of sqrt(100ms/1ms) = 10. Attila Kinali -- The bad part of Zurich is where the degenerates throw DARK chocolate at you. ___ 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.
Re: [time-nuts] Frequency Ensemble
On Sun, 17 Mar 2019 12:00:11 -0700 "Tom Van Baak" wrote: > So yes, NIST, USNO, PTB, BIPM -- all the big boys -- use ensemble > techniques. But the key is that they mostly use cesium clocks, not OCXO or > Rb clocks from eBay. Laboratory cesium standards don't suffer from frequency > drift. The other key is that the clocks are independent. Under these > conditions one can obtain sqrt(N) advantage. Most of the Cs beam standards contributing to TAI are 5071s. And, unfortunately, they do drift. As do almost all of the atomic clocks contributing to TAI. There are a handful of labs (IIRC 8) that run "the primary standards" which have a low enough uncertainty of influences to be considered non-drifting. IIRC all of them are are Cs fountains. Also unfortunately, most of these cannot or are not operated continuously. But according to METAS they don't need to be as the 5071s are stable enough that measuring their frequency once a month is enough to keep the uncertainty below what time and frequncy transfer can deliver today. Attila Kinali -- The bad part of Zurich is where the degenerates throw DARK chocolate at you. ___ 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.
Re: [time-nuts] Distribution amplifier for 10MHz and 1 pps
Yes :-) another one of mine: < http://www.hoffmann-hochfrequenz.de/downloads/iso_amp.pdf > It is based on a NIST design and made from discrete transistors. Unfortunately it also needs RF PNP transistors that are slowly going the way of the Dodo. Luckily, I still have a reel of BFG31. regards, Gerhard Am 17.03.19 um 19:00 schrieb Anders Wallin: I've tried to collect links to frequency/pulse distributor designs over here: https://www.ohwr.org/project/pda-8ch-fda-8ch/wikis/Similar-Projects if something good is missing let me know! AW > But how do I do this on 10MHz side? I'd like to have minimal distortion (sine wave) and high isolation. I acquired a few signal splitter and monolithic amplifiers. Split first and amplify? Amplify first and split? Remember it's only 2 to 3 channels. Amplifier module has too much gain, so I'll probably have to use attenuators. > ___ 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.
Re: [time-nuts] Distribution amplifier for 10MHz and 1 pps
> For 1PPs the main goal is jitter and the selection of the ICs is very tricky Could you please say more? Do you mean logic family selection, or chip selection within a family? Most modern digital chips are CMOS with an input threshold of VCC/2. I'd expect power supply noise to be important and families with faster switching times probably make more noise. -- These are my opinions. I hate spam. ___ 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.
Re: [time-nuts] Frequency Ensemble
> Hi Everyone,I like to know if it possible to run let say 10 GPSDO, 16 Rb clock > together and take the average to control 1 "master clock" and have better > stability ? > like what BIPM or NIST doing. > I have search about ensemble system but I have no idea how much advantage > I get from some clock that I already have.Thank You Anton Anton, The rule-of-thumb is that, *under the right conditions*, N clocks will perform sqrt(N) better than 1 clock. So yes, NIST, USNO, PTB, BIPM -- all the big boys -- use ensemble techniques. But the key is that they mostly use cesium clocks, not OCXO or Rb clocks from eBay. Laboratory cesium standards don't suffer from frequency drift. The other key is that the clocks are independent. Under these conditions one can obtain sqrt(N) advantage. The problem with using cheap OCXO or Rb clocks is that they drift, and this drift may depend on make / model / environment; all of which are possibly common mode for you. This means the full sqrt(N) assumption is likely not valid. The problem with using GPSDO is that they are not independent clocks. In fact, they aren't clocks at all: they are just noisy radio receivers, implementing "time transfer" from the USNO GPS master clock, which is related to but not equal to UTC(USNO) which is related to but not equal to UTC itself. There's a lot of common mode error amongst a set of GPSDO. This means the full sqrt(N) assumption is likely not valid. Those who use GPS for highest accuracy tend not to use GPSDO. Instead they just collect raw timing information and post-process it some hours to weeks later. That is, they want to know what time-it-was-precisely rather than what time-it-is-approximately. A GPSDO only does the latter. /tvb ___ 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.
Re: [time-nuts] Frequency Ensemble
Just a couple of other measurement options on top of Bob's excellent description. You could half the number of TICCs by using them in timestamp mode with a common 10 MHz clock serving as the reference -- in that mode you can do two simultaneous measurements with each TICC. There are some hardware and software hooks built into the TICC to allow multiple units to operate synchronously. (But we still need 25 orders :-) ). Second, as Bob mentions any PPS measurment is likely to be noisier at 1, 10, or 100 seconds than the sources you want to measure. If you decide to do one round of measurements every 1000 seconds, it's thoroughly practical to use some sort of switch matrix to measure each of the DUT in turn with a single TICC or other counter. In other words, once each 1000 seconds switch each DUT in turn to the TICC START input long enough to get one measurement. That's what I designed the TAPR TASS coax switch system for -- it lets you switch 8 DUT to one common output under USB control, and the controller supports up to 4 switches so you can make a really big matrix if you want (my setup at home has jacks for 24 DUT and 8 references). A project like this is ripe for all sorts of hardware hackery! John On 3/17/19 10:58 AM, Bob kb8tq wrote: Hi The answer is (of course) yes. The somewhat more detailed answer is that it actually is a practical basement sort of thing *if* you have the space. I was headed off to do this and changed course. That’s just my lack of focus rather than it being an un-doable sort of thing. What’s below is sort of a random walk through doing it. The first thing you need (after all the standards) is a way to do precision comparisons of all your devices. There are an infinite number of ways to do this. Let’s say you buy 26 TICC’s to do the job ( TAPPR needs 25 ordered to get the next batch going so that would solve two problems at once :) ). A PPS from a single source with good short term stability (maybe an OCXO) goes into one side of all of them. A pps from a DUT goes in the other side (yes there are other ways …TAPPR needs that order ….). You then have 26 devices each reporting how a single standard compares to the “main OCXO”. As. this chugs along you get a whole bunch of timestamps telling you how far your main OCXO is from each and every one of your “standards”. Since 10 of them are GPSDO’s they likely will be doing some very similar things. For the moment let’s ignore that and assume they are independent / uncorrelated sources. Since things like the Rb’s are free running data comes in spread out over the second, collecting data and comparing it isn’t exact. Once a second, you round up all the data and make a guess about what is correct. If everything is independent and equally noisy and … and … and … your guess could be sqrt(N) better than any individual source. With 26 sources, you would be a bit over 5X better than what you started with. You then diddle the EFC on an OCXO to put it inline with that estimate (yes that may mean a 27th TICC). Stepping back, there was a bit of hand waving going on there : One assumption is that the TICC measurement noise at one second is better than the noise of the sources. That probably is only true at much longer time spans (say >100 seconds). You can either upgrade the measurement or accept the longer time span. (TICC is about 1x10^-10 at 1 sec, 1x10^-12 at 100 sec, and 1x10^-13 at 1,000 sec) The “independent / uncorrelated sources” part is very suspect with a group of (possibly same manufacture) GPSDO’s in the mix. A burp here or there in the way GPS L1 (I’m guessing they are L1) is behaving can easily swing them all at the same time.. Things like temperature (Rb’s have temperature dependence) also can get into the mix. One alternate that might actually be easier to deal with: Run 10 free running OCXO’s and the 16 Rb’s. Add some number of GPS modules (with PPS outputs) to the mix. That way you will not be constantly fighting the unknown loop dynamics of the GPSDO’s. Next, somebody is likely to raise their hand and ask if the noise really *is* gaussian (and thus goes down as fast as the square root). The same things that get into making the sources correlated (and some other things) contribute to them being non-gaussian in this regard. Simple answer is you likely will not quite get to the 5X improvement advertised above. One thing you *can* do for some effects is try to learn them via cross comparison. That gets into the guts of your software and how you decide to do this. What the final result is at any specific tau will be very much a “that depends” sort of thing. The Rb’s have an ADEV curve that should drop by sqrt(tau). ( 10X better ADEV at 100X tau). Most GPSDO’s fairly flat ADEV out to some “hump” and then they follow GPS down from that point. If you actually steer an OCXO, the control loop will get into the act as well. You might also look into ganging up the TICC’s
[time-nuts] FTS-4040/A - Looking for voltage on switching power supply
I have an FTS-4040/A Cesium Oscillator from Datum. It was working last night and dead today. A/C available LED is lit but nothing else. Checking power supply, I read 8.9V. (large switching supply on back panel) Rather odd voltage I thought. Checked some ICs on a board. It's not getting power. Does anyone have this unit or know what this switching supply is supposed to output? It is a single voltage supply. --- (Mr.) Taka Kamiya I'm stuck in a wormhole Hello, worms! ___ 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.
Re: [time-nuts] Distribution amplifier for 10MHz and 1 pps
I've tried to collect links to frequency/pulse distributor designs over here: https://www.ohwr.org/project/pda-8ch-fda-8ch/wikis/Similar-Projects if something good is missing let me know! AW > > > But how do I do this > on 10MHz side? I'd like to have minimal distortion > (sine wave) and high isolation. I acquired a few signal > splitter and monolithic amplifiers. Split first and > amplify? Amplify first and split? Remember it's only > 2 to 3 channels. Amplifier module has too much gain, so > I'll probably have to use attenuators. > > > > > ___ 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.
Re: [time-nuts] Frequency Ensemble
Anton Others will reply but my sense is that there is little advantage in doing that. Assuming everything is the same in all 10 systems then you would be measuring the receiver behaviors at a given moment. I simply am unclear that there is an advantage. Regards Paul. On Sat, Mar 16, 2019 at 11:00 PM Anton Moehammad via time-nuts < time-nuts@lists.febo.com> wrote: > Hi Everyone,I like to know if it possible to run let say 10 GPSDO, 16 Rb > clock together and take the average to control 1 "master clock" and have > better stability ?like what BIPM or NIST doing. > I have search about ensemble system but I have no idea how much advantage > I get from some clock that I already have.Thank YouAnton > ___ > 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.
Re: [time-nuts] Frequency Ensemble
Hi The answer is (of course) yes. The somewhat more detailed answer is that it actually is a practical basement sort of thing *if* you have the space. I was headed off to do this and changed course. That’s just my lack of focus rather than it being an un-doable sort of thing. What’s below is sort of a random walk through doing it. The first thing you need (after all the standards) is a way to do precision comparisons of all your devices. There are an infinite number of ways to do this. Let’s say you buy 26 TICC’s to do the job ( TAPPR needs 25 ordered to get the next batch going so that would solve two problems at once :) ). A PPS from a single source with good short term stability (maybe an OCXO) goes into one side of all of them. A pps from a DUT goes in the other side (yes there are other ways …TAPPR needs that order ….). You then have 26 devices each reporting how a single standard compares to the “main OCXO”. As. this chugs along you get a whole bunch of timestamps telling you how far your main OCXO is from each and every one of your “standards”. Since 10 of them are GPSDO’s they likely will be doing some very similar things. For the moment let’s ignore that and assume they are independent / uncorrelated sources. Since things like the Rb’s are free running data comes in spread out over the second, collecting data and comparing it isn’t exact. Once a second, you round up all the data and make a guess about what is correct. If everything is independent and equally noisy and … and … and … your guess could be sqrt(N) better than any individual source. With 26 sources, you would be a bit over 5X better than what you started with. You then diddle the EFC on an OCXO to put it inline with that estimate (yes that may mean a 27th TICC). Stepping back, there was a bit of hand waving going on there : One assumption is that the TICC measurement noise at one second is better than the noise of the sources. That probably is only true at much longer time spans (say >100 seconds). You can either upgrade the measurement or accept the longer time span. (TICC is about 1x10^-10 at 1 sec, 1x10^-12 at 100 sec, and 1x10^-13 at 1,000 sec) The “independent / uncorrelated sources” part is very suspect with a group of (possibly same manufacture) GPSDO’s in the mix. A burp here or there in the way GPS L1 (I’m guessing they are L1) is behaving can easily swing them all at the same time.. Things like temperature (Rb’s have temperature dependence) also can get into the mix. One alternate that might actually be easier to deal with: Run 10 free running OCXO’s and the 16 Rb’s. Add some number of GPS modules (with PPS outputs) to the mix. That way you will not be constantly fighting the unknown loop dynamics of the GPSDO’s. Next, somebody is likely to raise their hand and ask if the noise really *is* gaussian (and thus goes down as fast as the square root). The same things that get into making the sources correlated (and some other things) contribute to them being non-gaussian in this regard. Simple answer is you likely will not quite get to the 5X improvement advertised above. One thing you *can* do for some effects is try to learn them via cross comparison. That gets into the guts of your software and how you decide to do this. What the final result is at any specific tau will be very much a “that depends” sort of thing. The Rb’s have an ADEV curve that should drop by sqrt(tau). ( 10X better ADEV at 100X tau). Most GPSDO’s fairly flat ADEV out to some “hump” and then they follow GPS down from that point. If you actually steer an OCXO, the control loop will get into the act as well. You might also look into ganging up the TICC’s to run 4 channels in one block. Unfortunately that would get the total order below what TAPPR needs … :) That would let you compare three standards against the master in one block and cut the total down to nine “pods” of two each. Indeed a fun project. There are a lot of papers out there on various aspects of it. Jim Barnes and David Allan authored a lot of them, either together or independently. Since they both worked at NIST, the papers are in the public domain. Have fun Bob > On Mar 16, 2019, at 9:16 PM, Anton Moehammad via time-nuts > wrote: > > Hi Everyone,I like to know if it possible to run let say 10 GPSDO, 16 Rb > clock together and take the average to control 1 "master clock" and have > better stability ?like what BIPM or NIST doing. > I have search about ensemble system but I have no idea how much advantage I > get from some clock that I already have.Thank YouAnton > ___ > 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://
Re: [time-nuts] Frequency Ensemble
> Le 17 mars 2019 à 02:16, Anton Moehammad via time-nuts > a écrit : > > Hi Everyone,I like to know if it possible to run let say 10 GPSDO, 16 Rb > clock together and take the average to control 1 "master clock" and have > better stability ?like what BIPM or NIST doing. I think the answer to this is probably no but it would make a nice project. I say no because your GPSDO will already be benefiting the from the clocks in GPS constellation that are being steered, probably indirectly) by the UTC(NIST) clocks, steered by the AT1 time scale, created from a whole bunch of cesium , maser and optical clocks , so your GPSDO is the equivalent of a master clock. This means that you only need one…well three to verify that one is not going on the blink. A GPSDO or Rubidium stability will probably be in the range of a few parts in 10^11 - 10^12. Measuring the phase offsets of a bunch go those and applying corrections to a another free running clock might buy you a zero but it is questionable I think. You are probably constrained by the quality of the chosen ‘master’. If there was a distinct advantage I would expect to see products on the market using this approach. I haven’t heard of any. > I have search about ensemble system but I have no idea how much advantage I > get from some clock that I already have.Thank YouAnton > ___ > 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. "Ceux qui sont prêts à abandonner une liberté essentielle pour obtenir une petite et provisoire sécurité, ne méritent ni liberté ni sécurité." Benjimin Franklin ___ 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.
Re: [time-nuts] Distribution amplifier for 10MHz
Ignacio, you will find it looking on Didier's page under 'manuals' and then searching e.g with 'steinmetz'. saludos, 73 Arnold, DK2WT Am 17.03.2019 um 12:15 schrieb EB4APL: Hi, It seems that Didier has changed his website somewhat and the links don't point to the referred documents. Either I was not able to find them navigating within the site. Regards, Ignacio, EB4APL ___ 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.
Re: [time-nuts] Distribution amplifier for 10MHz and 1 pps
The main problem in the distribution amplifiers for 10 Mhz is phase noise. There are two appoaches : the first one with a tuned amplifier like HP 5087A distribution amplifier. have a look at the manual the second one is the Racal 9478 wit phase locked VCO. For 1PPs the main goal is jitter and the selection of the ICs is very tricky On Sun, 3/17/19, Joakim Langlet wrote: Subject: Re: [time-nuts] Distribution amplifier for 10MHz and 1 pps To: "Taka Kamiya via time-nuts" Date: Sunday, March 17, 2019, 7:55 AM Hi, I used a monolithic amp for 10MHz (and 20 MHz) in my design. Since it is driven directly from a digital signal it uses a low-pass filter at its input. I used a Mini-circuits splitter at the output. I have enclosed a part of the drawing. In my case, I have two amplifiers (driven from two 180 degrees separated signals) and four outputs. The level at each output is high enough to use an external 1 by 4 splitter on the outside of the box. This gives me 16 possible 10 MHz signal to instruments. I have never used this many of course. Just as an example. Regards, Joakim Langlet (SM0OET) Den 2019-03-16 kl. 19:01, skrev Taka Kamiya via time-nuts: > Hello > I am thinking about distribution amplifier of a sort. Not a kind with 8 or more output but just 2 or 3. > > As you know, most timing equipment comes with just one output of a kind. Say one 10MHz and 1 PPS. This is rather inconvenient. If I want to scope it without disturbing the setup, I cannot. On my home brew Rb setup, I made sure I am going to put in 2 of each. > 1 pps was easy. Use 74HC04N. Signal comes into a register and to one inverter. Output of this inverter goes to all input of channel amplifiers. Each channel consists of parallel inverters with output going to resisters, then tied together. Works well. (amplifier meaning NOT gate) > > But how do I do this on 10MHz side? I'd like to have minimal distortion (sine wave) and high isolation. I acquired a few signal splitter and monolithic amplifiers. Split first and amplify? Amplify first and split? Remember it's only 2 to 3 channels. Amplifier module has too much gain, so I'll probably have to use attenuators. > > Have anyone run into this kind of thing? Is there an existing design? Anything anyone would like to share? > > --- > (Mr.) Taka Kamiya > I'm stuck in a wormhole Hello, worms! > ___ > 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. -Inline Attachment Follows- ___ 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.
Re: [time-nuts] Distribution amplifier for 10MHz
Yep, been there, done that! I used a modified Extron ADA 3-80, then replaced it with an ADA 6, both of which did have the CLC409 amps. Eventually, I replaced all with a real DA from Montronics (Fluke). Had to modify it for 10 MHz, since it maxed out at 5 MHz. Changing capacitors in tuned circuits fixed that problem, Using a Spectracom DA now, but I believe the old Montronics unit is a better DA. Might bring it back to life and see how they compare. Thanks for the trip down memory lane! Dave M - Original Message - From: "Charles Steinmetz" To: time-nuts@lists.febo.com Sent: Saturday, March 16, 2019 10:57:49 PM Subject: Re: [time-nuts] Distribution amplifier for 10MHz Dave M wrote: > Excellent advice from Charles, especially concerning isolation criteria. > Should you be looking to distribute a standard 10 MHz frequency to various > bench instruments, I'd recommend that you take a look at Extron video > distribution amps. Several models on Ebay right now, at reasonable prices. One particular series of Extrons is the subject of the modification instructions in my second link. One caveat -- there are at least two "generations" of Extron video DAs. Some have discrete circuits, and some are built using high-speed, high-current opamps (the now-obsolete Comlinear CLC409). The discrete circuits are all unmitigated CRAP. Horrible video DAs, unworkable as 10MHz/+13dBm DAs without major efforts and headaches. Absolutely not recommended. So, if you intend to convert an Extron video DA for 50 ohm use, make sure it is one based on high-speed opamps. To make everything just that little bit more fun, *NOTE* that Extron used some model numbers for first-generation discrete products and *re-used* the same model numbers for later-generation opamp products. One product number I'm sure this is true of is "ADA 3 180." Another may be "ADA 3 80." I'm pretty sure that all of the models named on the cover page of my modification instructions are opamp-only. Best regards, Charles ___ 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.
Re: [time-nuts] Distribution amplifier for 10MHz
Hi, It seems that Didier has changed his website somewhat and the links don't point to the referred documents. Either I was not able to find them navigating within the site. Regards, Ignacio, EB4APL El 17/03/2019 a las 4:57, Charles Steinmetz escribió: Dave M wrote: Excellent advice from Charles, especially concerning isolation criteria. Should you be looking to distribute a standard 10 MHz frequency to various bench instruments, I'd recommend that you take a look at Extron video distribution amps. Several models on Ebay right now, at reasonable prices. One particular series of Extrons is the subject of the modification instructions in my second link. One caveat -- there are at least two "generations" of Extron video DAs. Some have discrete circuits, and some are built using high-speed, high-current opamps (the now-obsolete Comlinear CLC409). The discrete circuits are all unmitigated CRAP. Horrible video DAs, unworkable as 10MHz/+13dBm DAs without major efforts and headaches. Absolutely not recommended. So, if you intend to convert an Extron video DA for 50 ohm use, make sure it is one based on high-speed opamps. To make everything just that little bit more fun, *NOTE* that Extron used some model numbers for first-generation discrete products and *re-used* the same model numbers for later-generation opamp products. One product number I'm sure this is true of is "ADA 3 180." Another may be "ADA 3 80." I'm pretty sure that all of the models named on the cover page of my modification instructions are opamp-only. Best regards, Charles ___ 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. --- El software de antivirus Avast ha analizado este correo electrónico en busca de virus. https://www.avast.com/antivirus ___ 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.
