Re: [time-nuts] overtone crystal question
Bernd, thanks for the excellent treatment on the subject glen On 21/09/2019 4:42 PM, Bernd Neubig wrote: Hi, There is nothing like a fixed ratio between R1 at 3rd or 5th overtone the R1 at fundamental mode. The best approach through C1 and Q. C1 reduces with the square of overtone N (for an infinite crystal plate). In reality C1(3rds about 85% of C1(fund/N^2. For the 5th and higher OT it is about 75 to 70% of C1(fund)/N^2.. Now Q comes into the game: The Q of a crystal designed for 3rd overtone is approximately s ___ 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] overtone crystal question
Hi Bob thanks for the insight. OK so the Rm for an overtone crystal , measured at the fundamental might be a bad indicator of the overtone Rm. I have found empirically, a loose relationship of Rm proportional to overtone number from the fundamental. But loose- I mean +/- 50% which, as you point out, may be optimized for the overtone, which is why my numbers are so far out cheers. On 19/09/2019 10:48 AM, Bob kb8tq wrote: Hi Bottom line - if you are designing a filter, you need the real values for the Cm, Lm and C0. Guessing at them is likely to lead to trouble if it is a reasonably complex filter. Rm generally goes as the overtone. It can deviate quite a bit from that (as can the other parameters) depending on how the blank is shaped and plated. ( If I want a good 3rd overtone, it will be designed to work well there. It may be pretty bad on the fundamental ….). Bob On Sep 18, 2019, at 2:35 PM, Glen English VK1XX wrote: I wonder if anyone can shed any light on this question, since this forum is loaded with those who REALLY understand crystals. I am modeling crystal filters (VHF) in SPICE. There are some specific acoustic mode models for SPICE in some Post Doctorial papers, very interesting, they would be the best but rather painful to use. However I using simplified Rm, Lm, Cm, Cs, Cp, Ccase etc My question is, how does Rm vary with overtone number ? My assumptions are Lm stays the same, Cm reduces proportionally to the square of the overtone number. Those assumptions are close enough and canon. I of course need the Rm number to acurately model loss. 73 glen english VK1XX ___ 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] overtone crystal question
I wonder if anyone can shed any light on this question, since this forum is loaded with those who REALLY understand crystals. I am modeling crystal filters (VHF) in SPICE. There are some specific acoustic mode models for SPICE in some Post Doctorial papers, very interesting, they would be the best but rather painful to use. However I using simplified Rm, Lm, Cm, Cs, Cp, Ccase etc My question is, how does Rm vary with overtone number ? My assumptions are Lm stays the same, Cm reduces proportionally to the square of the overtone number. Those assumptions are close enough and canon. I of course need the Rm number to acurately model loss. 73 glen english VK1XX ___ 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] TI LMK05318 clock sync
Anyone had a play with this device ? 1pps (or whatever) input, http://www.ti.com/lit/ds/symlink/lmk05318.pdf For those with a radio interest, or telecom interest.. I will order an eval board and see what its like... Yeah, I know its easy to do with a micro or fpga , but the phase noise from the internal VCO is impressive. I have no idea what the random stuff < 1Hz in adev territory is like. -glen ___ 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] atomic/chemical THz sampler / ZCDs
thanks all for the interesting answers on that one. and the notes on ZCDs was most useful. On 29/07/2019 ___ 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] atomic/chemical THz sampler
OK research people...since this forum is loaded with bleeding edge understanding, Is there such a thing in the lab as a material that can store, in a 2 level (1 bit) format (or more) , a discrete time representation of some event ? In my simple example (dream), an arrangement of some molecular or some quantum storage medium, that can store an event at discrete intervals of say, 100fs ? That is, the duration of the storage might be 1nS, storing the state of something, at 100fs intervals (example ) having a (for example) sample storage of 1 samples, and the ability to freeze that event (in some atomic level memory) for later readout once only or continuously looped ? No, I am not proposing this for my period /frequency analyser, I was just wondering about super high speed digitization and storage of very fast very short events. -glen ___ 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 Stability Analyzer - ZCDs
well. thank you everyone for your contributions ! I had a good night in reading the references. I agree the cascaded band-limited limiter strategy is eminently suitable. That LT part looks like an excellent option, of course, horses-for-courses caveat applies for freqs and risetimes... On comparators. Much of the 'noisyness' of comparators comes from the the use of a super wideband comparator say 5GHz, the noise in even a 50 ohm termination at room temperature is a few tens of microvolts and adds a fair bit of noise. I've dealt with this up to 500 MHz by filtering before comparison, but tricky for GHz ops... -glen On 28/07/2019 1:03 AM, Magnus Danielson wrote: Hi, Yes, indeed, so for many purposes the 6957 is probably good enough, and actually better than many classical approaches (i.e. direct comparators). It is when you design for a fixed or very narrow range of frequencies that you should consider rolling your own, assuming the performance of the 6957 becomes a limit to what you can achieve. Cheers, Magnus On 2019-07-27 15:49, Bob kb8tq wrote: Hi Assuming we are still talking about a test instrument that needs to handle a variety of levels and a range of frequencies, the 6957 is probably as good as anything. With a “full up” Collins style circuit, you very much need to optimize for a specific input. Change that and you change the circuit. 1 MHz, 10 MHz, and 100 MHz will each “want” a very different set of parts. Change levels 10:1 and that has an impact …. Even if you *do* get a circuit up and running, take a look at the TC of the caps in all those filter stages. Matching all that up for a valid test is going to be a bit hard. You have a wide range of values and (likely) a range of capacitor types. Not an easy problem to solve without ovenizing the whole beast. Do that and you no longer have a “simple” box … (and no guarantee a basic oven will solve the problem …) Bob On Jul 27, 2019, at 6:32 AM, Magnus Danielson wrote: Hi, On 2019-07-27 12:07, Attila Kinali wrote: On Sat, 27 Jul 2019 18:21:50 +1200 (NZST) Bruce Griffiths wrote: The LTC6957 is a better choice for squaring up sinewaves: http://www.ko4bb.com/getsimple/index.php?id=phase-noise-and-other-measurements-with-a-timepod If you want to have a single component ZCD, then I agree. Otherwise, a multi-stage Collins like ZCD can perform better. Especially, if the input waveform has known properties, then the multi-stage approach can properly optimize for those. The LTC6957 is a multi-stage device with only 4 different bandwidths to optimize for, so you can do better. It may however be good enough for many purposes. Comparators are almost always noisier. Oliver Collins wrote a paper on optimising such sine to square converters. I extended the analysis to allow optimisation when the input noise of the cascaded stages arent equal. There is one important point with Collins' analysis that hardly gets mentioned: His analysis assumes that the output signal of a stage is trapezoid. While this is true for high gain settings, it is not for low gain settings. Ie in his example with 6 stages, the first three stages have a total gain of 23, ie the signal has still significant curvature. Thus Collins' analysis the noise contribution of these three stages contains significant erros. See the attached paper for details. The trapetzoid model is a simplification which is better than sine or square, but not perfect. Another thing with Bruce noticed was that it assumed the same noise from all op-amps, but you can choose different op-amps with different noise and slope-rates and then you need different formulas, which Bruce produced. Additionally, in a multi-stage ZCD, it is very important to keep the duty cycle at 50%, as otherwise the even harmonics give rise to an increase of flicker noise due to noise up- and down-conversion. See [1] for details. This effect has been seen by NIST for dividers, which made them conclude one needs to end with a divide by 2. Cheers, Magnus Attila Kinali [1] "A Physical Sine-to-Square Converter Noise Model", by Attila Kinali. 2018. http://people.mpi-inf.mpg.de/~adogan/pubs/IFCS2018_comparator_noise.pdf ___ 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
Re: [time-nuts] Frequency Stability Analyzer - ZCDs
Hi there is quite a bit done in this area of FPGAs, IDELAYS etc for this application. and also quite a bit written already on TIMENUTS I find from archives. From my POV, the pressure on the design is the input circuitry...My gut is to start with a ADCMP572 and drive several FPGA pins with PECL or CML . BUT ! I have not thought about the problem very much, nor do I have much experience with this application (and trying to be a little modest here considering the company I am in) . The temperature variability of the comparator hysteresis might be some issue with the comparator. I think the FPGA method certainly has many limits , compared to the analog methods (dual slope phase comparators driving 24 bit ADCs etc, vernier methods.) But my intuition is that a design that can leverage a hybrid of analog methods and some handy features available in modern FPGAs can get the performance. The idea is, to produce a general purpose high performance measurement platform for HF region clocks, and pps, without having to resort to buying an SR620.. analog front end, FPGA (VHDL) , drive for a standard HD44780 LCD controller to display stuff, and output (USB most likely) for data analysis on a platform that has plenty of storage. IDELAYS - there is good granuality (26ps Artix -1) (3 ps Ultrascale Kintex) , temperature stability is a bit average but that can be dealt with. The IO delays are variable on the fly for some architectures. It is not the whole story, but one of the bullets in the revolver in acheiving the desired granuarity. There are several calibration options. jitter added in the routing can be minimize with some manual placement strategies There is an additional handle at the place and route level on specifying constraint delays. This is pretty rough but if a good calibration strategy can be developed, it is worthwhile. (IE conformance to the constraint delays may vary from build to build so there needs to be a bit of manual placement ) . Yes, I think trace delays are useful, although rise time of the devices together with PCB bandwidth muddies the water , and hence uncertainty etc etc I'd like to use a Lattice MACH X02 for this job but I think I will use a Xilinx due to my familiarity with them (and indeed, performance and control of the synthesis tools) , and the speed. (i'm actually an RF person but FPGAs and DSP is an essential these days) . -glen On 27/07/2019 11:49 AM, Hal Murray wrote: Was considering 16 LVDS receivers and IDELAYS to emulate a single fast comparator, I haven't done serious work with FPGAs in 10 or 15 years. That seems like an obvious hack, but it depends on the implementation details inside the FPGA. What's the granularity? How much does it change from chip to chip or over voltage and temperature? Has anybody published any data? -- Another possibility is to use trace delays on the PCB. You have a lumped delay line with capacitance from the input pad. This may not be practical for short delays where the bond wires on the chip are not short relative to the trace lengths. ___ 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] Frequency Stability Analyzer - ZCDs
I'm currently getting schematics together for just such a box, to be open source etc. maybe it can be a TAPR project I dunno. I'll release round 1 schematics shortly. Most of my ZCD work to this point usually uses LVDS receivers either discrete or FPGA IOBUF and more lately the ADCMP572 for a 7 GHz undersampling project. Was considering 16 LVDS receivers and IDELAYS to emulate a single fast comparator, since there is jitter anyway on the ADCMP572>> FPGA fabric connection. that jitter is not so much of a problem for my 7 GHz undersampling apps, but in applications where performance on a 1pps matters, with a 1 second observation , might need a different approach. Happy to incorporate / use suggestions for what people what from this forum... glen On 27/07/2019 5:02 AM, Tom Van Baak wrote: Yes, I'm evaluating a FSA3011 at the moment. It's a cute little unit. Documentation is sparse, the jpg plots are fuzzy, "customer" support is nil, but it works. My initial tests show it's ~4x worse than the data sh ___ 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] time nuts symposium
So, is there anytime once a year or two years where members of this group get together ? I guess many of the professionals here go to their own respective industry meetings . Like we all do. Rub shoulders with Rubiola etc. glen ___ 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] AN/URQ-10A - on frequency doublers
good info Rick ROY - I have spiced up in LTSPICE a doubler and 4 harmonics which you can vary the amplitudes of the harmonics in the current sources I1, I2, I3, I4. There is a basic tank circuit on the output which you can connect/ disconnect etc. www.cortexrf.com.au/5_meg_doubler.asc Rick , you are right the harmonics on the source really do mess with it... you could also do a digital frequency doubler. that's easy, dependson ur jitter spec.. . or a PLL using a DBM as a phase detector with a regenerative divider if you really want to knock yourself out. many cats and skins cheers On 18/07/2019 11:54 PM, Richard (Rick) Karlquist wrote: The 5071A has a chain of doublers from 10 to 320 MHz. One thing I learned in designing this is that it is important to drive the doublers with pure sine waves. It might seem like if I double from 10 to ___ 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] uBlox F9P versus F9T
fine business. thanks for the insight. The dual band L1, L2 is a certain plus. At a price Hard to ignore the benefits certainly for apps that can afford it. I'll report back... cheers On 18/07/2019 7:37 AM, Bob kb8tq wrote: Hi Having played with both, there are differences in how the P and the T do things. Both do a better job on timing than single band modules do. The T has multiple pps outputs and *should* handle logging (at a fairly coarse resolution) an input pps on two inputs. Both will handle external correction inputs via a serial port. The P does not do SBAS, but the T does. They now say that SBAS degrades timing on the T (as it does on all other receivers) so that may not be a plus. I have not checked the latest firmware on the T, but with the last version, the P actually delivered better timing performance. Indeed it was running defaults so SBAS likely running at the time. If you are trying to do some sort of master / slave setup, it’s best to dive into just what is involved with that task. For a system where both master and slave are mobile, the P is likely the better choice. Bob On Jul 17, 2019, at 4:57 PM, Glen English VK1XX wrote: The F9T and F9P - are these interchangeable for stationary timing use and stationary high performance position ? From how I read the datasheets, : the F9P has an internal RTK engine, and the F9T outputs the info RTCM etc and that data can be run on a external RTK engine on a micro. The P provides 1.5m standalone positional accuracy compared to the T standalone positional accuracy of 2.0m. Not much difference there.. the F9P and F9T have their timing pulse performance shown using different description. The P has this as "RMS and 99%", while the T has this as '5nS','2.5ns diff' Both can operate with companion receivers to enhance performance but I interpret this as only the P can do a (internal, companion mode) differential position fix and only the T can do a (internal companion mode) differential time fix. That is , internally without using an external engine. *** So it seems, if using an external RTL etc engines, the devices can do roughly the same thing. How do others interpret this ? I want to do projects using positional for one app, and timing for another, and would like to be able to acheive the deep quantity discounts... glen ___ 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] AN/URQ-10A - on frequency doublers
Roy, The passive frequency doubler is essentially perfect. It will add some flicker noise. (There are documented methods like using CB connected transistors etc however I suggest just build it unless you are after doing better than the best labs in the world). For all passive freq doublers, depending on where it is going, you might want some selectivity to reject 4f, 6f etc , and also duty cycle affects you might need to take notice of.The sort of input level you have available, 3 to 10dBm is fairly suitable. Expect conversion loss of 10 to 12dB , start with +10 is a good place. You will most likely need some amplification post doubling to get back where you want to be. ...could buy off the shelf : I would suggest this one : The balance is good ensuring low odd harmonics : https://www.minicircuits.com/WebStore/dashboard.html?model=RK-3%2B For easy construction , for your 5 MHz doubler, I would suggest two RF transformers and a bridge like this: (schematic at the page) - see figure 4. https://www.qsl.net/4f5aww/module5k.htm you can use a centre tapped transformer, or 3 wire transformer. OR, you could use a bridge frequency doubler has a little better non even harmonic rejection... page 13: https://www.qsl.net/va3iul/Frequency_Multipliers/Frequency_Multipliers.pdf glen On 18/07/2019 8:07 AM, Roy Thistle wrote: Hi All: I tried to search for this, in the forum, but, I didn't find much. I'm interested in getting a AN/URQ-10A... I have the manual. It's an old on ship, frequency standard. Does anyone have recommendations, or issues, concerning these units? The one I am thinking of is a little bit high (about +10 Hz, I think) and can't be "tuned" back to 5 MHz, without... I am guessing calibration. But, I am wondering if... because of the positive drift, if the crystal is damaged. By the way, how and why 5MHz... because its not that useful! … at least today. Does a frequency doubler… assuming a lock on the standard... cause errors in the 10 MHz signal obtained? Best regards and wishes Roy ___ 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] uBlox F9P versus F9T
The F9T and F9P - are these interchangeable for stationary timing use and stationary high performance position ? From how I read the datasheets, : >>the F9P has an internal RTK engine, and the F9T outputs the info RTCM etc and that data can be run on a external RTK engine on a micro. The P provides 1.5m standalone positional accuracy compared to the T standalone positional accuracy of 2.0m. Not much difference there.. >> the F9P and F9T have their timing pulse performance shown using different description. The P has this as "RMS and 99%", while the T has this as '5nS','2.5ns diff' >>> Both can operate with companion receivers to enhance performance but I interpret this as only the P can do a (internal, companion mode) differential position fix and only the T can do a (internal companion mode) differential time fix. That is , internally without using an external engine. *** So it seems, if using an external RTL etc engines, the devices can do roughly the same thing. How do others interpret this ? I want to do projects using positional for one app, and timing for another, and would like to be able to acheive the deep quantity discounts... glen ___ 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] GPDSO Distribution amp that does not radiate ?
This sounds like a shield is not connected , or broken on one of the distribution cables. The 10 MHz will not appreciably leak from half decent coax properly terminated. The 10 MHz should not be detectable unless a wire is coupled directly on the coax braid. That assumes the 10 MHz source itself is well shielded and all wires that enter or exit are firewalled . is this an attempt to distribute square or sine wave 10 MHz ? -glen On 14/07/2019 2:53 AM, Jerry O. Stern wrote: I have been using a Tbolt and TAPR TADD-1 for a few years, mainly as an external reference source for my workbench equipment. Just got a SDR radio kit (Ubitx) and trying to calibrate the local oscillators found this annoying substantial 10MHz signal heterodyning with the LO's (45MHz and 12MHz). Taking a look on my SA with just a broad band telescopic antenna in the SA input, I see a 10MHZ at about -55 dBm and no other signals > -120 dBm. The Tbolt is about 4-5' away from the workbench BUT I disconnected everything and it is only connected to the TADD-1 distribution amplifier The TADD has no distribution coaxes attached, it is in the TAPR metal cabinet which I always thought was well shielded and every port has been terminated with 50 Ohm dummy load plugs. When I take the TADD-1 out of the equation and just run the Tbolt into a 50 ohm termination plug, the 10MHz signal on my SA drops down to > -90 dBM. I duplicated this with a Lucent RFTGm-Xo/Rb pair and the TADD-1 with similar results.Has anyone else seen this with their distribution amp? Jerry ___ 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] Neural net to control oven temperature ?
Hi Chase thanks for the email. thanks for the tip on use of logistical classifiers. Agreed the PID (and variations ) is a seemingly perfect fit , at least at the top level.. My guess is that the type of disturbance the 'the system' (affecting, ultimately, the set temperature) (the device) could be classified (in real time) as a cause of different mechanisms, and for a specific mechanism, there might be a more optimal solution to minimize error. My primary intrest in these things looking at new ways to do old things better.. I like systems that predict the error that is coming, before it occurs...so I like adaptive filter driven control systems . I am slowly getting my head around alpha-beta and Kalmans as time permits. The most popular neural net function is of course computers playing games- feed it the history of 10,000 games and as Chase says, it figures out the patterns of Y in a sea of X If anyone is interested in this stuff, you dont need to buy a dev kit. You can do it all in Python. Or C . Once you understand the basics , it is easy enough to program. If you dont understand the basics, you might not be able to acheive a desired outcome. There are quite a few good books on these subjects for Python for those interested. I wish I could go back to school and do a year or two on this stuff... glen On 10/07/2019 12:23 PM, Chase Turner wrote: Hi Glen, This is actually something I know a little about. Neural nets are most useful for feature selection, that is, finding the important x that is a function of y, in a very large sea of x variables. In this case, we already know what's important, which is temperature stability. So, a neural net would be a bit much when we already know what feature is important for function. Additionally, unless I'm mistaken, oven control is probably a linear relationship of some sort or another, and neural nets are much better suited for examining and revealing insights about non-linear data. If you have a method by which you can collect the necessary data that has a bearing on the oven functionality, you'd probably be better off training a logistic classifier, and using it instead. That said, both methods would be overkill, imo- I'd use a PID instead. Best, Chase On Tue, Jul 9, 2019 at 10:00 PM Glen English VK1XX < glenl...@pacificmedia.com.au> wrote: Has anyone tried to use a Neural net to control oven tmep, rather than the ye olde PID ? IE the algorithm learns from previous beheviour and successfully predicts behaviour (or not). I'm sure there are a few out there proficient with machine learning algorithms. Might make a good masters thesis I bet. Given that oven control based on inputs and whatever is not random, unlike say flicker etc. glen ___ 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] Neural net to control oven temperature ?
Has anyone tried to use a Neural net to control oven tmep, rather than the ye olde PID ? IE the algorithm learns from previous beheviour and successfully predicts behaviour (or not). I'm sure there are a few out there proficient with machine learning algorithms. Might make a good masters thesis I bet. Given that oven control based on inputs and whatever is not random, unlike say flicker etc. glen ___ 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] Advantages of GNSS ???
and non monitonicity in the device is the death of a control loops. My attempts at building good OCXOs using cheap AT crystals in the 90s was thwarted by non monotonic bending crystals ! And everytime they would wake up, the monitonicity would be in a different part of the control curve and they exhibited hysteresis, like defined steps , this seems to be the case with most crystals, the harder you looked, the more undesirable imperfections you found... On 10/07/2019 5:57 AM, David G. McGaw wrote: Leo - I do believe you mean non-monotonic, rather than non-monotonous. Not being monotonous is a good thing. :-) David N1HAC On 7/9/19 1:20 PM, Leo Bodnar wrote: It's not very good, it is highly non-linear and even wor ___ 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] LT3042, etc. Re: HP E1938A schematics.
RRR . you are right about drop and noise.. For others not familiar with this behaviour, one thing when looking is PSRR etc on LDOs..take a good look at this value VERSUS dropout / headroom . Most devices are in the toilet when dropout is nigh... In my SDRs I (used) to run 2V around for 1.8V point of load LDO supplies. PSRR 100k went up alot when I bumped the supply rail to 2.2V... On 9/07/2019 10:44 AM, jimlux wrote: On 7/8/19 4:53 PM, Richard (Rick) Karlquist wrote: On 7/8/2019 11:09 AM, jimlux wrote: Not only are they low noise, but they have spectacularly good HF rejection across the regulator up to 10s of MHz. In the 5071A, I wanted high bandwidth PSRR and stumbled across a designer's manual (HP internal document) for the MMS Modular Measurement System. They described a regulator with a common base pass transistor and an op amp, with a bandwidth approaching 1 MHz. Quite state of the art for the time. I copied the design in several 5071A modules. We used it to regulate +5V from the Vicor modules down to ___ 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] E1938A source code/ firmware
OK so I have the NGOCOMM program for the E1938A. I see looking at the DLLs it was written in Borland OWL. Does anyone have the C++ source code, or know what is in it , and also does anyone know exactly what is in the E2PROM? all this for extending the MAINTAINABLE life of these excellent OCXOs. -glen ___ 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] A Research Proposal
with regard to phase angle and confusion over load and power flow ... I think people getting confused with the phase of measured current to the voltage . the voltage phase is fixed, and should be consistent . when you measure the current phase, relatve to the voltage, that tells you about the flow (and PF) So using a AC-AC filament transformer and a fast opto on the secondary , with some care that it doesnt saturate the transistor to slow the turnoff, in a nice thermally controlled environment, seems suitable. -glen ___ 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] A Research Proposal
In Australia, we have a national grid. It's big. National meaning all but a few isolated towns like Darwin, Perth. Perth might be connected via a 1800 km HVDC line in the future... which is a different story DC interconnectors So, I gather someone with their MASER in Adelaide could compare their MASER to the 50 Hz over some period, and provide the relative offset of the grid to others, so others in australia also observing and averaging over some period , could get a useful frequency reference from their wall socket. -which I gather is what people do , since i am new to this timing game. That would have its limits depending on the ADEV of the mains . and the use of DC interconnectors. -glen On 8/07/2019 11:21 AM, Bob kb8tq wrote: Hi The whole “phase here vs phase there” thing was at the heart of the papers the power guys started presenting back in the late 1980’s …. A ___ 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] HP E1938A schematics.
Hi Rob Thanks for the post. wow. OK thanks for the notes. No expense spared anywhere on the quality of those parts used. mine are Rev Bs EEPROM. might need to read out that info while it is good. Probably important parameters what goes wrong with these babies ? or should I consult the list archives ? -glen On 8/07/2019 3:50 AM, Rob040 . wrote: Hi, I've made some new schematics of the HP E1938 oscillator/controller module. I derived them from the HP schematics that I found on Brooks' site. The aim was to have more clear versions for service/repair. They should reflect the situation as they left the factory, what isn't on the PCB isn't present in the drawings (not sure about the content of the oscillator 'puck'). It's the version with the 20P connector on the component side. ___ 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] Multiple OCXO (topic changed from E1938A )
Hi Bob, and Achim . thanks for the comments. I've change the subject line to fit more in line we the morphed discussion. Good discussion, and like Bob said, there will be lots of common mode on the GPSs. The diurnal GPS derived clock errors due to the ionosphere are well described . Bob thats a good point about picking and choosing, and long term effects. My initial obs on two devices, tell me there IS significant non-correlated noise between two of them, but this is on low cost GPS and also I have not yet established how much noise is purely my edge point sampling errors and nothing to do with the actual device, and the two in question have different views of the sky Acbom, you have clearly thought about this. As for the IDELAYS etc, IDELAYS yes have been used for this sort of thing since the mid 90s. Enough of them and enough inputs and some known waveform to compensate against, and some differential means, should be enough to mitigate the temperature/process effects. If rising and falling edges are worked, delay will affect both and compensate. While 1pps source might usually be only accurate on one edge, nothing an external ECL / GaAs flip flop won't fix to provide 1/2 pps. One can also use PCB delay...150ps per inch... being careful of FR4 weave , zig zags etc.although once the rise time of the signal gets amongst the delay we want, thats uncertainty. *** Assuming we end up with a single, nice clean compensated and as good as possible timebase (from 1pps etc) (sounds like your territory, Bob), and With multiple OCXO ( ALL being simultaneously inter-dependently disclipined ) , there may be the opportunity to try different parameters (or even algorithms) on the different OCXOs and pick the one with the minimum squared error (or something like that) . What might kill that is that the OCXOs vary quite alot even on the same model. The goal of this is a) to learn something- precision instrumentation is hard. b) have a 1e-13 accurate long term (weeks on) frequency reference c) have short term 1000 second stability <= 1e-12 glen On 7/07/2019 6:56 PM, Achim Gratz wrote: Glen English VK1XX writes: ___ 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] Switching 1 pps signal
In that case, my suggestion is think of them all as transmission lines in coax. terminate as needed. Others here will also have points I have missed I am sure, or alternative equally valid suggestions. beign critical (maybe I am being over critical) : watch out also for reflections from unterminated (open ) relay contacts, the 2x pulse you might get back at the driver might cause harm or trouble on the supply rail. IE so source terminate ideally, even if it costs you a little swing or at least a little series R like 10 ohms source R to mop up reflections back on the source... if its swinging 2V with source term = 10 ohms into 51 ohms, that wont hurt too much. rather than just totem pole strong CMOS driver , consider LVPECL style driving, also. IE it depends what drivers and receivers you choose simple would be all 1.8V CMOS I guess, most stronger buffers will drive 50 ohms and 1.8V if you plan on multiple drop, then you'll need to consider where you place the termination... which is why differential rocks over single ended because the swing can drop before the trouble develops with double termination. of course if you AC couple into single ended setups that can work but messy. glen On 7/07/2019 2:07 PM, Taka Kamiya via time-nuts wrote: I should have mentioned this clearly earlier, but all converting and switching, then measuring happens in ONE 2U rack case. Length of each cable is minimal. I thought mention of TICC would make it sort of clear but it didn't. I have LOTS of coax relays. I'll use them. It's a gross overkill but I've seen 80s HP equipment have overly generous parts selections, too. It's hard to explain EXACTLY as the contraption isn't built yet. That made it necessary to use generic terms. I apologize for causing confusion. --- (Mr.) Taka Kamiya KB4EMF / ex JF2DKG On Sunday, July 7, 2019, 12:00:52 AM EDT, Glen English VK1XX wrote: Hal, Good point. and I have never seen a spec for phase stability for Cat-7 cable ! for RG58, OR OTHER polyethylene, might be up to 150ppm /deg C. maybe as good as 10 ppm/deg C for some LMR. With 1000 feet of cable might be an issue for fine stuff. a few nano seconds each way over temperature might not matter for his project... I forget it is not a microwave RF VNA application. Easy to resolve anyway with a difference balance term somewhere. g ___ 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] Switching 1 pps signal
Hal, Good point. and I have never seen a spec for phase stability for Cat-7 cable ! for RG58, OR OTHER polyethylene, might be up to 150ppm /deg C. maybe as good as 10 ppm/deg C for some LMR. With 1000 feet of cable might be an issue for fine stuff. a few nano seconds each way over temperature might not matter for his project... I forget it is not a microwave RF VNA application. Easy to resolve anyway with a difference balance term somewhere. g On 7/07/2019 11:23 AM, Hal Murray wrote: coax cables are in general NOT PHASE STABLE with temperature, either. Is twisted pair any better? ___ 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] Switching 1 pps signal
I thoroughly agree with Bob. Suggest converting 1pps into something hardy like LVDS or LVPECL and using twisted pair , Cat 7 (individually shielded pairs and controlled skew cable) , or a pair of coax (balanced coax). The balanced signals will deal with the chance of power supply differences, and attach the shields of the balanced pairs to local ground with 10nF caps of something If there are different earth potentials at each end (different power circuits), where the differential receivers end up running out of common mode headroom, the balanced signals will work nicely with ethernet transformers . (LF caveat) . coax cables are in general NOT PHASE STABLE with temperature, either. or if lightning is a problem, convert and drive a fibre optic . that's another story, you can use the SFP modules that have GHz of bandwidth but be wary of their internal optical AGC and thus may not extend to DC. glen. On 7/07/2019 8:52 AM, Bob kb8tq wrote: Hi Indeed the fast rise time of just about any modern digital signal gets energy up into the GHz region. Isolation wise, the simple answer is often to just disable the signal when not in use. In a one at a time system, that takes care of cross talk / feed through. There are a lot of “always on" devices out there that suffer from blips on (say) the 10 MHz output each time the (maybe) 1 pps edge goes out …. disabling signals at the sourcre isn’t always an option. The other half of the problem is how to get the signal to its destination when it *is* in use. Coax (with some sort of drive that will handle a 50 ohm load) is usually the answer for long runs. For shorter runs simple twisted pair works ok. For very short runs a trace on a board or a jumper wire may be all you need. So now, what are the dimensions on all those really vague terms? Long (as in coax) is up into the 10’s of feet and down range. Shorter (as in twisted pair is in the 5 feet and down range, with a foot or two being pretty safe. Anything in the “couple inches” range is territory for a wire or simple trace on a board. The two issues (isolation and integrity ) are not completely independent of each other. In many cases you both need isolation *and* a good signal. In those cases, the mumble mumble mumble lengths above get a bit shorter. Just how short depends on just how good the isolation needs to be. Coax runs in the “under a foot” range are not unheard of. Further complicating this is the fact that you can get fancy twisted pair setups that are fine for longer runs. You can get really crummy coax that isn’t good for anything. There are always ways to route traces or bundle wires that will get you in trouble. Lots of fun and lots of rabbit holes to wander down …. 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.
Re: [time-nuts] E1938A source code/ firmware
OK, good info, thanks. Well I have bought 7 x E1938As, with the intention of building a better GPSDO. My interest in the E1938A firmware hex was if I had to replace any of the PICs at sometime in the future. My intention is to use the average of multiple stationary mode GPS 1PPS signals to drive a single OCXO, the idea to be a better 1pps estimate. I'll upsample the inputs to get the control sample rate up. Eventually I want to explore the use multiple OCXOs, but not until I think of a good way to take an average of multiple OCXOs, or, even if that is a useful idea. FPGA based, I'll put the OCXO drive and the 1ppS to the FPGA differentially into maybe 8 FPGA inputs (that is each signal into 8 different FPGA pin pairs) , and use IDELAY blocks to delay the 8 different inputs to provide more edge resolution for each signal . The IDELAY blocks can be dynamic but I'll probably use then fixed. output of the FPGA can be sigma-delta converter, which can provide almost arbritary number of bits. LVDS output of the 1 bit FPGA converter signal will go to an outboard LVDS buffer with its own power supply so bumps on FPGA VCCIO dont affect the output. So first, I'll need to build a frequency/period counter in the same ilk (same PCB) I'll make these PCBs loaded available to all. I have a protoype built and output at the moment is HD44780 LCD drive 8 bit bus to surplus 40x4 char displays I have around here. and also a serial stream output. best to do only what is necessary on the FPGA (rudimentary time/frequency output onto the LCD) , and feed data to an analysis machine, RPI, PC whatever for analysis and display in Python 2.7X. comments welcome. -glen VK1XX / AI6UM On 6/07/2019 10:06 PM, Adrian Godwin wrote: I would agree that antiwindup is important when you have integrators. They always seem to cause trouble without it, in applications as diverse as car throttle control and time-domain filtering of respiratory data. I would also recommend, sometimes, the use of feed-forward control to provide an estimate of power demand without relying on the integrator : although most useful for speeding the response, it can also reduce th ___ 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] Are there any company selling refurbished/reconditioned Cesium tubes?
thanks Corby, and all, for their beam tube buying advice. On 7/07/2019 4:34 AM, cdel...@juno.com wrote: When evaluating an instrument with a used tube the beam current is not the best indicator to look at! For an HP instrument If the tube label has the EM voltage listed then with the beam current set to it's proper level check the current EM voltage. As the tube ages you will require more and more EM voltage to bring the gain back to nominal. Also performing a SN test on the tube or even a quick look at the peak/valley/background levels is helpful. Cheers, Corby ___ 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] E1938A source code/ firmware
Hi Rick Thank you very much for the reply and the suggested leads. I think your work on the balanced bridge oscillator was both preeminant and seminal . I have read all the papers on it, and there are few other things in my 30 years of this field professionally that really impress me as much in the new approaches and new thinking on the entire unit. Agreed on the PII^2D control system. I've built a few OCXOs back in the 90s, the best I did on (inner) oven control was using dual glass bead thermistors in a bridge configuration with lots of gain driving a simple opamp integrator. The opamp was chopper stabilized and I ensured the op amp never operated in the crossover region of the opamp output driver. These were on AT cuts at 97 deg C ... cheers Glen. AI6UM / VK1XX On 6/07/2019 2:37 PM, Richard (Rick) Karlquist wrote: On 7/5/2019 8:20 PM, Glen English VK1XX wrote: Has anyone got this , is the PIC read data prohibited ? Is it still a closely guarded secret?, there were some very clever and novel ideas used in that slab, in my opinion. Glen Hi Glen. I worked on this project, but am an RF/Analog guy. The product line was sold to Symmetricom 20 years ago and they didn't continue the E1938A. At that point, there were no closely guarded secrets. I don't know what happened to the source code. The last contract manufacturer for the E1938A was Scotts Valley Magnetics. You could contact them and see if they have the PIC info. In theory, they would have had to have it to program the PIC's. The most clever thing in the PIC (AFAIK) is the oven controller with the double integrator. "P, I, I^2, D". Len Cutler was the mastermind behind this. I believe he leveraged his experience with double integrators used in Cs control loops. I remember him telling me that the secret was to have an "anti-windup" algorithm. Whatever he did, the results were phenomenal. I spent countless days in the lab exercising the loop and it always worked perfectly. Rick Karlquist, N6RK ___ 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] E1938A source code/ firmware
Has anyone got this , is the PIC read data prohibited ? Is it still a closely guarded secret?, there were some very clever and novel ideas used in that slab, in my opinion. Glen ___ 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] Are there any company selling refurbished/reconditioned Cesium tubes?
Bob, thanks for the info. I will immerse myself in the archives. regards, glen. VK1XX / AI6UM On 1/07/2019 11:15 PM, Bob kb8tq wrote: Hi There are a lot of posts back in the archives about various things on Cs standards. Beam current is probably the best way to see ___ 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] Are there any company selling refurbished/reconditioned Cesium tubes?
Bob, are there any URLs you can point to, or provide advice on, if inspecting a Cesium for sale, is there an hour counter, or other metrics that can be measured in the tube department ? (I am familiar with TWTs, Klystrons etc so the HV doesnt bother me) in order to ascertain the level of life left ? that is, apart from turning it on and waiting a while and measuring ADEV for a week on the sellers premises. glen On 1/07/2019 7:09 AM, Bob kb8tq wrote: Hi Based on several replacements on a “high performance” 5071 …. 6 to 7 years of 24/7/365 seems to be about the point things start to get flakey. Maybe not dead, but crazy enough that it lets you know it needs a new tube ( = ADEV is not even close to what it should be ..). Cost several years back for the swap out was right at $40K. The process included hazmat shipping silly nonsense. That part delayed the process by almost 2 months. 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.
Re: [time-nuts] Subject: Re: GPS 1PPS, phase lock vs frequency lock, design
Hi Bob RRR. In fact all my original GPSDOs in the '90s were FLLs, for radio comms gear, essentially frequency counters with the error driving a PI loop. They were controlling standard XOs. For new engineers, if they want a project to teach them many skills, I recommend a GPSDO project from scratch, there are many excellent disclipines to grasp, oscillators, control systems, measurement and many systematic errors to understand... and the project is only done if the spec is met, and of course the spec can go on being as tight as you want. You could spend your whole life on it. glen On 25/06/2019 1:16 PM, Bob kb8tq wrote: Hi In a GPSDO, an FLL can be done with no “cycle slips” between readings. In that case, the I term will indeed correct for long term errors. The net result will be effectively the same as a PLL for long term error. That is by no means to say that *all* FLL’s are done this way. Only that it is one possible implementation. 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.
Re: [time-nuts] Subject: Re: GPS 1PPS, phase lock vs frequency lock, design
Leo is right Depends on the application. Phase lock for 1pps to trigger say, simultaneous capture of many radio telescopes around the globe is a good need for phase lock to a source. Frequency lock might suit many . change of phase between two sources might indicate frequency change, or duty cycle change. For all my digital PLL and digital FLL implementations, the method of capturing the data is identical... just the transfer function of the filter is different. So they are nearly indistinguishable. A choice might depend on the control loop bandwidth, and whether the initial error (acquisition) is beyond the BW. In those cases depending on the type of comparison, it might make sense to measure the frequency error, and then move the (controlled) source within phase lock without cycle slip range in one step. Useful for very long time constants and large initial errors. ...and then what do you do when including relativistic effects ... glen. On 25/06/2019 3:42 AM, Leo Bodnar wrote: Hi Dana, I am just saying that, properly implemented, PLL and FLL are indistinguishable as long as output signal is concerned while lock is present and that the phase slew at regaining lock in PLL loop is counterproductive for one but necessary evil for others. I have a feeling that FLL is looked down upon by general public ever since PLL became a household term. In a well designed PID loop "I" term makes sure that you don't have "permanent but varying error." All my messing about with loops, holdovers and recovery was pretty much with your application in mind. Cheers! Leo Are you saying that you want to abandon phase lock altogether in favor of freq lock? Or just during the reacquisition following loss of and restoration of the reference? By me definition of pure freq lock, there will generally be some permanent (but varying) frequency error, so that phase error could accumulate without limit; clearly an undesirable thing in most applications. My interest lies in having a stable LO for receiving, without accumulating phase error (at least during times of missing reference). When the reference goes away, I'll accept some phase error accumulation. So for me, I think the best approach is phase lock under normal circumstances, but switch to freq lock during reacquisition of phase lock. DanaK8YUM ___ 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.
