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] A Research Proposal
On 7/8/19 7:05 PM, Dana Whitlow wrote: I'm surprised that the VF of HV transmission lines is noticeably less than unity, given that the dielectric is just air. Or does the distributed resistance do all the damage? It's all about L and C that creates the delay - propagation constant is proportional to 1/sqrt(L*C), Z is sqrt(L/C) So you see those funky delay line coaxes with Z=1000 ohms - a spiral center conductor(with a magnetic core) jacks up the L. Check out the link to the lecture notes I had... ___ 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 ???
One what? I see that it is a Ublox unit, but see no reference to the interesting modern units like the 9 series. Also, I note that the only reference on the board to "ant" is on the lower right corner, while what I suppose to be the actual antenna connector appears to be an SMA near the upper right corner. And why does it look like several of the components have been resoldered or replaced or something? Dana On Mon, Jul 8, 2019 at 8:00 PM ew via time-nuts wrote: > Well now you can see one > Bert Kehren > > > In a message dated 7/8/2019 7:02:07 PM Eastern Standard Time, > hol...@hotmail.com writes: > > A big issue with using the sawtooth correction message from a GPS > receivers is the issue of just what that sawtooth value is related to and > how to apply it to the measured PPS value / phase. > I added the ability to Lady Heather to calculate a sawtooth corrected > "paper clock" by applying the sawtooth correction message value to the PPS > output measured by an external counter like the TAPR TICC. > > There are around a dozen different combinations of sawtooth value and PPS > measurements... only one of which minimizes the PPS error. Do you add or > subtract the sawtooth value to the PPS measurement? Do you apply the > sawtooth value to the previous/current/next PPS measurement? Do you apply > the sawtooth correction to the PPS itself or the accumulated phase of the > PPS? > I don't think that I have ever seen what to do with the sawtooth value > documented in any receiver documentation... Heather has default receiver > dependent correction strategies or lets you specify the correction > strategy to use.___time-nuts > mailing list -- time-n...@lists.febo.comTo unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.comand 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] A Research Proposal
I'm surprised that the VF of HV transmission lines is noticeably less than unity, given that the dielectric is just air. Or does the distributed resistance do all the damage? Dana On Mon, Jul 8, 2019 at 8:00 PM jimlux wrote: > On 7/8/19 3:11 PM, Hal Murray wrote: > > > > glenl...@pacificmedia.com.au said: > >> I think people getting confused with the phase of measured current to > the > >> voltage . > > > > No, we have been discussion the phase angle between 2 geographically > separated > > locations connected by a power line. > > > > Consider the simple case of a generator, 100 miles of line, and then a > light > > bulb. The voltage at the light bulb will be delayed by the speed of > light. > > That delay can be expressed as a fraction of a cycle and converted to a > phase > > angle. > > > > > It gets much more complicated if you have multiple generators, multiple > loads, > > and various transmission lines, and even more complicated when you turn > things > > on and off. > > > The transmission line is decidedly not Velocity Factor =1.0 > > A typical propagation constant might be j0.0018/mile > > about 5500 km/wavelength at 60 Hz. > > Free space propgation delay for 5500 m is 18.5 milliseconds - compared > to 16.67 millisecond period of 60Hz. A velocity factor of about 90% > > (that's for an example I found for 765 kV, using Tern conductors, in > bundles of 6 > > http://home.engineering.iastate.edu/~jdm/ee552/Transmission.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.
Re: [time-nuts] Recommendations for time beginner?
Long winded answer to your question: I'm sort of an "Advanced beginner" time-nut or maybe a bit beyond that. In relation to your question: It really depends on your goals. The following is a high level overview of your options, and is intentionally lacking and/or simplifying some details. There are lots of twists and turns one can go down on each of these options. And there's a few spots which I'm making generalizations which may or may not be exact. In the way of "precision" 10Mhz clock sources, I have 2 thunderbolts, a PRS-10 rubidium oscillator, and a BG7TBL GPSDO. Oh and a couple/few OCXO's which are undisciplined. I want a cesium clock but haven't happened to end up with one yet. You're somewhat familiar with the thunderbolts, let me compare the others first. The OCXO's are undisciplined, but aren't that bad of a 10Mhz reference. Especially if you can trim them to a good quality reference - such as your thunderbolt. Depending on your needs, this might be good enough for you. Generally, once the OCXO is warmed up you can adjust it to match the reference, then as long as it isn't shut off it should stay very close to the same frequency. Of course it will drift over time and perhaps as a result of other external forces (temperature, humidity, voltage, vibration, etc). Of course you can then re-trim it to the right frequency. How much and how often you need to do this will depend on the oscillator. A surplus OCXO can be had for well under $100. A good quality pre-aged surplus one is likely better than a new out of the box one (even of the same time). Other members of the list have much more experience with which are the best, but I personally have found that the oscilloquartz ones are typically acceptable for my needs. A rubidium oscillator is like an OCXO on steroids. But if you think of it as a very very very low drift OCXO then you've probably got the right idea. For comparison a good OCXO will drift in a day about the same as a rubidium will drift in a year. You can often get a Stanford PRS10 in good condition for around $250 or so. The challenge is that any atomic clock has a certain limited life due to the physics package "wearing out" in some form or another, so it's a bit higher risk than just buying a good quality OCXO. Before I get to the GPSDO's let me mention about the relative ease of trimming the above two types of references. If you have a two channel oscilloscope, it is rather easy to trim these. You plug the reference clock into one channel, set the scope to trigger off of that channel (so the waveform is stable). Then you plug the clock you are trimming into the second channel. You then adjust or 'trim' the oscillator until the waveforms do not move (or beat) in relation to each other. If you don't have a two channel oscilloscope, there are other ways to do this as well. Now back to the GPSDO's. The thunderbolt you have is a OCXO 'disciplined' by the GPS's 1PPS output. It's the same as trimming the OCXO on a continual basis such that the OCXO output always has 10 million cycles per 1 second. There are other GPSDO's that use other types of oscillators as well (rubidium, vcxo, etc). The method of trimming the oscillator varies from GPSDO to GPSDO, but the effect is typically the same: that is to adjust the 10Mhz output to something close to 10Mhz. As I mentioned I have a trimble thunderbolt and a BG7TBL GPSDO. The BG7TBL GPSDO is a GPSDO designed by a Chinese ham, and each edition seems to be a little different, typically using a u-blox GPS receiver and seemingly whatever surplus OCXO they can get their hands on. Mine happens to have a russian OCXO in it. The quality of these seem to be rather good, although there is a bug which affects mine and other earlier ones which cause the long-term frequency to be very slightly off. The very slightly off means it runs at ~9.9 Mhz instead of 10Mhz.I beleive that There are other designs out there as well from other vendors. A search on a certain popular auction site for "GPSDO" reveals a lot of options. I've had discussions with a couple of people who have compared several of these and apparently the consensus is that they're typically all decent for general use, and some are better than others, but none that they've tried are especially bad. Certainly they should be good enough for a reference clock for most people. If I didn't have a collection of oscillators already I'd probably pick up 1-2 of these of varying types. Maybe a thunderbolt and one of these. One final caveat, which may or may not be applicable to you: In some applications, certain types of noise can be a problem. Depending on how you're using the clock you may actually find that a disciplined oscillator is not the right solution. Generally I'm timestamping events and I'm more interested in stability instead of precision. So, even if the frequency of my clock source is off by 1-2% it isn't a big
Re: [time-nuts] LT3042, etc. Re: HP E1938A schematics.
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 +4.5V working voltage for 100 series ECL or analog. It worked quite well. Now I could replace it with an LT3065. Rick N6RK Barely - I've got bit in the past by coming too close to the LDO minimum voltage. 300mV for those parts, so as long as your +5 had decent regulation, and the ripple didn't drop below 4.8V, and you didn't draw more than 300 mA. ___ 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.
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 +4.5V working voltage for 100 series ECL or analog. It worked quite well. Now I could replace it with an LT3065. Rick 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.
Re: [time-nuts] A Research Proposal
On 7/8/19 3:11 PM, Hal Murray wrote: glenl...@pacificmedia.com.au said: I think people getting confused with the phase of measured current to the voltage . No, we have been discussion the phase angle between 2 geographically separated locations connected by a power line. Consider the simple case of a generator, 100 miles of line, and then a light bulb. The voltage at the light bulb will be delayed by the speed of light. That delay can be expressed as a fraction of a cycle and converted to a phase angle. It gets much more complicated if you have multiple generators, multiple loads, and various transmission lines, and even more complicated when you turn things on and off. The transmission line is decidedly not Velocity Factor =1.0 A typical propagation constant might be j0.0018/mile about 5500 km/wavelength at 60 Hz. Free space propgation delay for 5500 m is 18.5 milliseconds - compared to 16.67 millisecond period of 60Hz. A velocity factor of about 90% (that's for an example I found for 765 kV, using Tern conductors, in bundles of 6 http://home.engineering.iastate.edu/~jdm/ee552/Transmission.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.
Re: [time-nuts] Advantages of GNSS ???
Well now you can see one Bert Kehren In a message dated 7/8/2019 7:02:07 PM Eastern Standard Time, hol...@hotmail.com writes: A big issue with using the sawtooth correction message from a GPS receivers is the issue of just what that sawtooth value is related to and how to apply it to the measured PPS value / phase. I added the ability to Lady Heather to calculate a sawtooth corrected "paper clock" by applying the sawtooth correction message value to the PPS output measured by an external counter like the TAPR TICC. There are around a dozen different combinations of sawtooth value and PPS measurements... only one of which minimizes the PPS error. Do you add or subtract the sawtooth value to the PPS measurement? Do you apply the sawtooth value to the previous/current/next PPS measurement? Do you apply the sawtooth correction to the PPS itself or the accumulated phase of the PPS? I don't think that I have ever seen what to do with the sawtooth value documented in any receiver documentation... Heather has default receiver dependent correction strategies or lets you specify the correction strategy to use.___time-nuts mailing list -- time-n...@lists.febo.comTo unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.comand 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] A Research Proposal
glenl...@pacificmedia.com.au said: > I think people getting confused with the phase of measured current to the > voltage . No, we have been discussion the phase angle between 2 geographically separated locations connected by a power line. Consider the simple case of a generator, 100 miles of line, and then a light bulb. The voltage at the light bulb will be delayed by the speed of light. That delay can be expressed as a fraction of a cycle and converted to a phase angle. It gets much more complicated if you have multiple generators, multiple loads, and various transmission lines, and even more complicated when you turn things on and off. -- 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] Advantages of GNSS ???
A big issue with using the sawtooth correction message from a GPS receivers is the issue of just what that sawtooth value is related to and how to apply it to the measured PPS value / phase. I added the ability to Lady Heather to calculate a sawtooth corrected "paper clock" by applying the sawtooth correction message value to the PPS output measured by an external counter like the TAPR TICC. There are around a dozen different combinations of sawtooth value and PPS measurements... only one of which minimizes the PPS error. Do you add or subtract the sawtooth value to the PPS measurement? Do you apply the sawtooth value to the previous/current/next PPS measurement? Do you apply the sawtooth correction to the PPS itself or the accumulated phase of the PPS? I don't think that I have ever seen what to do with the sawtooth value documented in any receiver documentation... Heather has default receiver dependent correction strategies or lets you specify the correction strategy to use. ___ 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] It is possible to "recharge" a hydrogen maser?
The model of H Maser is KVARZ: CH1-75A. Thank you for the replies friends! Soon here in the lab we will start to discuss the maintenance. Best regards Luiz Em sáb, 6 de jul de 2019 às 22:01, Jim Palfreyman escreveu: > Hi Luis, > > I have experience with the NASA NR series if that’s what you have. Blue and > about the size of a household fridge, wth lovely 80s red LEDS on the front. > > If it is this model, I’d expect it is more likely that your ion pump(s) > need replacing. > > I can send all the documentation you need. > > Jim > > > On Sat, 6 Jul 2019 at 3:01 am, Luiz Paulo Damaceno < > luizpauloeletric...@gmail.com> wrote: > > > Hi friends, > > > > We have a hydrogen maser here at the university that i work. It seems the > > hydrogen is over. This is possible? If yes, It is possible to recharge > It? > > > > Best regards, > > > > Luiz. > > ___ > > 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] 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] Advantages of GNSS ???
Hi Whatever they are doing to create an output is being done modulo the internal TCXO period. That gets you down to a +/- 4 ns error on either the F9T or the F9P. They can do that however often they like, it’s still a very coarse correction as far as I’m concerned. What matters is how often they come up with the data to tell you how far off from reality that magic edge *is* in reality. They do that to well under a nanosecond, both on the F9T and the F9P. That update info only is calculated / supplied once a second. This information *plus* the edge is (at lest to me) the only source of accurate time out of the device. It’s at least 10X better than what you get without the correction If indeed you *do* configure to let them modify the TCXO <-> pulse output at a greater rate than once a second, the connection between the sawtooth correction data and the actual pulse becomes a bit obscure. Only one edge has data for it. The rest have an offset of “who knows what”. Having a bunch of “unknown” edges in with one accurate one seems like a route to confusion. This all gets right back to the recommendation that I quoted about running the pulse rate at 1 pps for precision use. There are similar notes in similar documents going back at least to the LEA-5T era of modules. Are any of them 100% clear - nope. You have to either call up and ask “what does this really mean?” or guess a bit. Is this a knock of some sort on uBlox? Certainly not. No document ever written is ever going to be perfect. They are not the only outfit doing this (one second calculation of error). They aren’t any worse at explaining it than the other guys. They all do a pretty good job of describing what’s going on face to face. Bob > On Jul 8, 2019, at 9:51 AM, Leo Bodnar wrote: > > Bob, what are you calling "time correction"? > > You are now quoting F9T which is not the product original statement related > to (F9P.) > > If you refer to internal Ublox adjustment of instantaneous timepulse train > then it is performed at navigation rate - up to 20Hz on F9P. > F9P's rate of TP can be set from 0.25Hz to 10MHz according to the datasheet > but in reality is usually wider. > > TP edge quantisation is a separate issue to TP base rate adjustment and it is > done at TP rate. > > Leo > > >> Subject: Re: [time-nuts] Advantages of GNSS ??? >> They go absolutely crazy updating nav?.. but they only come up with the >> timing correction once a second. >> >> From the latest version of the F9T Manual UBX-19005590 - R02 on page 43: >> The recommended configuration when using the UBX-TIM-TP message is to set >> both the measurement rate (CFG-RATE-MEAS) and the time pulse frequency >> (CFG-TP-*) to 1Hz. >> >> Since the rate of UBX-TIM-TP is bound to 1 Hz, more than one UBX-TIM-TP >> message can appear between two pulses if the time pulse frequency is set >> lower than 1 Hz. In this case all UBX-TIM-TP messages in between a time >> pulse T1 and T2 belong to T2 and the last UBX- TIM-TP before T2 reports the >> most accurate quantization error. In general, if the time pulse rate is not >> configured to 1 Hz, there will not be a single UBX-TIM-TP message for each >> time pulse. >> >> Sorry if the quote comes through a bit garbled. Sometimes this cut and paste >> stuff does not quite do the trick. >> Indeed it?s not 100% clear what they are doing from the docs. They say this >> and that here and there. The >> bottom line is still that you can only trust the sawtooth offset data to be >> correct at the one second point. >> >> Bob > > > ___ > time-nuts mailing list -- time-nuts@lists.febo.com > To unsubscribe, go to > http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com > and follow the instructions there. ___ time-nuts mailing list -- time-nuts@lists.febo.com To unsubscribe, go to http://lists.febo.com/mailman/listinfo/time-nuts_lists.febo.com and follow the instructions there.
[time-nuts] Recommendations for time beginner?
Hi, I'm extremely new to the topics covered on this list, but am finding reading the message traffic to be highly educational. I have some questions that I'd like to put out, and apologize in advance for them being at a greatly simpler level than most of the discussion here. I came to time-nuts by way of an interest in frequency measurement as a radio ham. To supply a 10 MHz signal to my gear I bought a used Trimble Thunderbolt. I always like to have a backup, so am thinking of obtaining another device (either a GPSDO or something else that can provide a 10 MHz signal). For a beginner, is there something else that offers accuracy/precision at least as good as a Thunderbolt and doesn't cost more than a few hundred dollars at most that you might recommend? I also have some questions about using the Trimble, but will put those in a separate message. Thanks, Frank O'Donnell ___ 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] verifying synchronization with PPS
s...@eskimo.com said: > My specific question concerns the case that one of the boxes is a computer, > for example, a Linux box with time kept using ntpd or chrony (perhaps also > listening to a PPS signal coming in on a serial port). But I've never seen a > computer with a PPS *output*. There is code in the Linux kernel to generate a PPS output. I've never tried it. I think it uses the printer port which isn't available on modern systems. You can probably get a PCI plugin card. You will probably have to build your own kernel. If I wanted to try something, I would write a user-level hack to flap a modem line and compare that to a PPS signal. The code would look something like this: t1 = time() set line low t2 = time() set line high t3 = time() log t2 and t3 wait 1/2 second set line low wait 1/2 second loop The first time/set is to warm out the cache. > (Perhaps PPS is overkill for this situation; perhaps it's the case that given > the inherent inaccuracies of software-based timekeeping, a software-based > query mechanism -- perhaps using ordinary NTP or PTP protocols -- would be > sufficient for That just gets time from one computer to another. Now you have the same "is it right?" question on another box. -- 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] verifying synchronization with PPS
From: Steve Summit [] My specific question concerns the case that one of the boxes is a computer, for example, a Linux box with time kept using ntpd or chrony (perhaps also listening to a PPS signal coming in on a serial port). But I've never seen a computer with a PPS *output*. = Steve, Folkert van Heusden has a driver for NTP which includes PPS output: https://vanheusden.com/time/rpi_gpio_ntp/ Perhaps this might help? Cheers, David -- SatSignal Software - Quality software for you Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk Twitter: @gm8arv ___ 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] LT3042, etc. Re: HP E1938A schematics.
On 7/8/19 8:38 AM, Richard (Rick) Karlquist wrote: Regarding the E1938A schematic: Although not references per se, the LT3042/LT3045/LT3045-1 are extremely low noise voltage regulators. Actually, if there are any time nuts who haven't yet heard of these, the data sheets should be considered required reading. Recently, ADI introduced a family of negative regulators that are basically exact mirror images of the positive regulators, right down to the same pin out. The LT3093 is a negative version of the LT3042 and the LT3094 is a negative version of the LT3045-1. ADI has done an outstanding job of supporting the chips with reference designs and PC board layout tips along with evaluation boards. Not only are they low noise, but they have spectacularly good HF rejection across the regulator up to 10s of MHz. I highly recommend them. They appear to be reasonably radiation tolerant, too, although not advertised as such. ___ 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] verifying synchronization with PPS
Several comments: What level of accuracy do you mean by "synchronized"? Plotting a lightly loaded Linux box, which is extracting time from the network via timesyncd, against a GPS 1PPS signal, I observe typical time excursions within +/- 10 ms, and extreme excursions over a 24 hour period of up to 20 ms. So, I would not count on network based time on a Linux box to be better than +/- 20 ms, probably worse with heavy loading of the OS. A simple navigation GPS receiver PPS output, without any additional corrections can provide accuracy of less than 0.1 microsecond. The owner of this list has designed an excellent dual input timing device called the TICC, which can compare two PPS signals with resolution of 8 or 9 decimal places, for projects like this. https://tapr.org/kits_ticc.html --- Graham == On Mon, Jul 8, 2019 at 9:03 AM Steve Summit wrote: > This is a different sort of question than what seems to be > discussed here usually, and I apologize if it's wholly off-topic, > but I'm guessing there are some time nuts here who might be able > to give me some pointers. > > If I have two boxes with clocks that are supposed to be perfectly > synchronized, and I need to verify this, and they're physically > right next to each other, and they both have PPS outputs, one > way to verify the synchronization would be to compare the two PPS > outputs with a 'scope. (I'm guessing there's probably a dedicated > instrument out there specialized for the task of comparing two > such PPS signals for frequency, phase and jitter, and if I were > a proper time nut myself I guess I'd know that.) > > My specific question concerns the case that one of the boxes is > a computer, for example, a Linux box with time kept using ntpd > or chrony (perhaps also listening to a PPS signal coming in on a > serial port). But I've never seen a computer with a PPS *output*. > > Is this a reasonable thing to be thinking about, or am I going > about it wrong? How would *you* positively verify synchronization > of such a system? Me, I'm pursuing this idea because too much > of the time (at least in my own, perhaps parochial experience) > synchronization seems to be "verified" either by saying "Yes, > we configured it properly", or by observing a status output > from ntpd or chrony claiming the requisite synchronization > has been achieved, but in neither case by making a definitive, > independent, external, empirical determination. > > (Perhaps PPS is overkill for this situation; perhaps it's the > case that given the inherent inaccuracies of software-based > timekeeping, a software-based query mechanism -- perhaps using > ordinary NTP or PTP protocols -- would be sufficient for > externally assessing synchronization.) > > I guess it's not a *completely* unreasonable thing to be thinking > about, because I've found a couple of web pages (for example > https://www.raspberrypi.org/forums/viewtopic.php?t=115554 and > https://github.com/jsln/pps-gen-gpio) describing how to implement > a PPS output under Linux. And I do realize that trying to > minimize the jitter and latency in this situation (given that > the principal drivers for the hypothetical output are inherently > software-based) presents considerable difficulties. But taking > all of that into consideration, I'm wondering what others think > of the approach. Thanks for any comments. > > ___ > 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] verifying synchronization with PPS
Steve, I'm curious: in the absence of a PPS or other electrical output from your "computer", what is the nature of the time "output "? If it's just visual via a display, why not view the light output of the seconds digit with a photocell. Most of the transitions should produce an easily-detectable step or glitch in the light. Dana On Mon, Jul 8, 2019 at 9:03 AM Steve Summit wrote: > This is a different sort of question than what seems to be > discussed here usually, and I apologize if it's wholly off-topic, > but I'm guessing there are some time nuts here who might be able > to give me some pointers. > > If I have two boxes with clocks that are supposed to be perfectly > synchronized, and I need to verify this, and they're physically > right next to each other, and they both have PPS outputs, one > way to verify the synchronization would be to compare the two PPS > outputs with a 'scope. (I'm guessing there's probably a dedicated > instrument out there specialized for the task of comparing two > such PPS signals for frequency, phase and jitter, and if I were > a proper time nut myself I guess I'd know that.) > > My specific question concerns the case that one of the boxes is > a computer, for example, a Linux box with time kept using ntpd > or chrony (perhaps also listening to a PPS signal coming in on a > serial port). But I've never seen a computer with a PPS *output*. > > Is this a reasonable thing to be thinking about, or am I going > about it wrong? How would *you* positively verify synchronization > of such a system? Me, I'm pursuing this idea because too much > of the time (at least in my own, perhaps parochial experience) > synchronization seems to be "verified" either by saying "Yes, > we configured it properly", or by observing a status output > from ntpd or chrony claiming the requisite synchronization > has been achieved, but in neither case by making a definitive, > independent, external, empirical determination. > > (Perhaps PPS is overkill for this situation; perhaps it's the > case that given the inherent inaccuracies of software-based > timekeeping, a software-based query mechanism -- perhaps using > ordinary NTP or PTP protocols -- would be sufficient for > externally assessing synchronization.) > > I guess it's not a *completely* unreasonable thing to be thinking > about, because I've found a couple of web pages (for example > https://www.raspberrypi.org/forums/viewtopic.php?t=115554 and > https://github.com/jsln/pps-gen-gpio) describing how to implement > a PPS output under Linux. And I do realize that trying to > minimize the jitter and latency in this situation (given that > the principal drivers for the hypothetical output are inherently > software-based) presents considerable difficulties. But taking > all of that into consideration, I'm wondering what others think > of the approach. Thanks for any comments. > > ___ > 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] HP E1938A schematics.
Regarding the E1938A schematic: I will try to answer your questions when I have time. Watch this reflector. The story on the voltage reference is: The original part I chose turned out to be too noisy. I selected a different, quieter part for the final design. I don't remember the MPN's of each reference. If you are curious, I would advise looking at the actual PCB and reading the number off the IC package. Now that 20 years have passed, that IC may or may not still be available in the original package or in any package, and in any event, there are now probably better references available. Although not references per se, the LT3042/LT3045/LT3045-1 are extremely low noise voltage regulators. Actually, if there are any time nuts who haven't yet heard of these, the data sheets should be considered required reading. Recently, ADI introduced a family of negative regulators that are basically exact mirror images of the positive regulators, right down to the same pin out. The LT3093 is a negative version of the LT3042 and the LT3094 is a negative version of the LT3045-1. ADI has done an outstanding job of supporting the chips with reference designs and PC board layout tips along with evaluation boards. Rick N6RK On 7/7/2019 10:50 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. I made a One DAC and Two DAC version and made a separate sheet for the power supply, otherwise I wouldn't fit on one sheet (format is A2). Please feel free to use it, you can find the package attached to this mail. Because I didn't open the oscillator module, I'm not sure about the following things: - In the voltage reference section: C65 (100nF) is in parallel with a 0 ohm resistor (R74), so I expect C65 is not present on the PCB. Is "No load" in this case the same as "Not mounted"? - In the input of the amplifier section: R28 (0 ohm) is in parallel with potmeter (R77) of 50 ohm. No clue which of both is present. - The capacitance mention on the label of the 'puck', where is it placed in the circuit? Is it one of the C2/C3 which has a fixed value of 100pF in the schematic? Or is it in parallel with CR1 (the BB512)? Or is it like I drew in the oscillator part (bridge section)? - Type of U5 (Vref IC) is still unknown, anyone knows which type it is? Best regards, Rob Tromp ___ 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] A Research Proposal
Andy, it appears to me that the FNET/GridEye system already does what you propose: http://fnetpublic.utk.edu The Angle Contour Map displays the kind of results you desire. But it doesn't know the Western Interconnection at this time. I believe there is a typo at the top of the Angle Contour Map: > The frequency gradient map visualizes the real-time angle "differences" with > respect to a referential point in Eastern > Interconnection. Shouldn't that state: "The ANGLE CONTOUR MAP visualizes ..."? According to the legend, the angle contour map displays a measure of the phase angle differences between the individual FDR hosts and a "referential point". I'm not sure if that is an actual specific FDR host or some averaged phase. Of course, you need to think carefully in a relativistic manner when you are trying to look at local phase in locations so far apart. At 60 Hz (in the US) 1 degree of phase corresponds to 46.3 us. That's the free space propagation delay of light over 13.89 km (8.63 miles). Generators 777 miles apart have a 90 degree phase relationship with respect to free space propagation phase. -- Bill Byrom N5BB Irving, TX On Mon, Jul 8, 2019, at 6:11 AM, Andy Backus wrote: > To clarify: > > My research proposal is for data to be taken within the same interconnection. > > It does not care about frequency. > > It does not care about Time Error. > > It only seeks to characterize the phase differences between the power > line signal presented in regions of the distribution system separated > by significant geographical distances. > > 180-degree phase reversals and three-phase transformations along the > chain of information are easily distinguishable. > > Thanks for your interest. I hope some will accept the technical > challenge of gathering data -- which is fairly minimal. > > Andy Backus > Bellingham, WA > (Western Interconnection) > > ___ > 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] verifying synchronization with PPS
This is a different sort of question than what seems to be discussed here usually, and I apologize if it's wholly off-topic, but I'm guessing there are some time nuts here who might be able to give me some pointers. If I have two boxes with clocks that are supposed to be perfectly synchronized, and I need to verify this, and they're physically right next to each other, and they both have PPS outputs, one way to verify the synchronization would be to compare the two PPS outputs with a 'scope. (I'm guessing there's probably a dedicated instrument out there specialized for the task of comparing two such PPS signals for frequency, phase and jitter, and if I were a proper time nut myself I guess I'd know that.) My specific question concerns the case that one of the boxes is a computer, for example, a Linux box with time kept using ntpd or chrony (perhaps also listening to a PPS signal coming in on a serial port). But I've never seen a computer with a PPS *output*. Is this a reasonable thing to be thinking about, or am I going about it wrong? How would *you* positively verify synchronization of such a system? Me, I'm pursuing this idea because too much of the time (at least in my own, perhaps parochial experience) synchronization seems to be "verified" either by saying "Yes, we configured it properly", or by observing a status output from ntpd or chrony claiming the requisite synchronization has been achieved, but in neither case by making a definitive, independent, external, empirical determination. (Perhaps PPS is overkill for this situation; perhaps it's the case that given the inherent inaccuracies of software-based timekeeping, a software-based query mechanism -- perhaps using ordinary NTP or PTP protocols -- would be sufficient for externally assessing synchronization.) I guess it's not a *completely* unreasonable thing to be thinking about, because I've found a couple of web pages (for example https://www.raspberrypi.org/forums/viewtopic.php?t=115554 and https://github.com/jsln/pps-gen-gpio) describing how to implement a PPS output under Linux. And I do realize that trying to minimize the jitter and latency in this situation (given that the principal drivers for the hypothetical output are inherently software-based) presents considerable difficulties. But taking all of that into consideration, I'm wondering what others think of the approach. Thanks for any comments. ___ 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 ???
Bob, what are you calling "time correction"? You are now quoting F9T which is not the product original statement related to (F9P.) If you refer to internal Ublox adjustment of instantaneous timepulse train then it is performed at navigation rate - up to 20Hz on F9P. F9P's rate of TP can be set from 0.25Hz to 10MHz according to the datasheet but in reality is usually wider. TP edge quantisation is a separate issue to TP base rate adjustment and it is done at TP rate. Leo > Subject: Re: [time-nuts] Advantages of GNSS ??? > They go absolutely crazy updating nav?.. but they only come up with the > timing correction once a second. > > From the latest version of the F9T Manual UBX-19005590 - R02 on page 43: > The recommended configuration when using the UBX-TIM-TP message is to set > both the measurement rate (CFG-RATE-MEAS) and the time pulse frequency > (CFG-TP-*) to 1Hz. > > Since the rate of UBX-TIM-TP is bound to 1 Hz, more than one UBX-TIM-TP > message can appear between two pulses if the time pulse frequency is set > lower than 1 Hz. In this case all UBX-TIM-TP messages in between a time pulse > T1 and T2 belong to T2 and the last UBX- TIM-TP before T2 reports the most > accurate quantization error. In general, if the time pulse rate is not > configured to 1 Hz, there will not be a single UBX-TIM-TP message for each > time pulse. > > Sorry if the quote comes through a bit garbled. Sometimes this cut and paste > stuff does not quite do the trick. > Indeed it?s not 100% clear what they are doing from the docs. They say this > and that here and there. The > bottom line is still that you can only trust the sawtooth offset data to be > correct at the one second point. > > 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] A Research Proposal
> I hope some will accept the technical challenge of gathering data -- which is fairly minimal. Andy, It may have been before you joined time-nuts, but some years ago we compared mains phase/frequency between Albuquerque, NM and Seattle, WA, which in spite of being some 1500 miles apart are on the same grid. Another test was between two nearby locations, Bellevue, WA and Redmond, WA. All data was taken by timing zero-crossings to the microsecond with a picPET. You'll find the results fascinating: http://leapsecond.com/pages/mains-cv/ I'm happy to repeat any of this analysis using recent data from Hal (CA), and you (Bellingham, WA), and me (Bellevue, WA). A third test which is interesting is comparing independent mains phase/frequency between different rooms of the same house. In general you want to understand local house effects, then neighborhood effects, then city / country effects before you jump into interstate grid effects. It's similar to establishing baselines and noise floors when you make precision clock measurements. /tvb On 7/7/2019 11:49 PM, Andy Backus wrote: To clarify: My research proposal is for data to be taken within the same interconnection. It does not care about frequency. It does not care about Time Error. It only seeks to characterize the phase differences between the power line signal presented in regions of the distribution system separated by significant geographical distances. 180-degree phase reversals and three-phase transformations along the chain of information are easily distinguishable. Thanks for your interest. I hope some will accept the technical challenge of gathering data -- which is fairly minimal. Andy Backus Bellingham, WA (Western Interconnection) From: time-nuts on behalf of Dave ZL3FJ<2c...@silverbears.nz> Sent: Sunday, July 7, 2019 9:23 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] A Research Proposal I have here a pair of instruments that were part of a system used at one time in a power station here in NZ to control the time error in one part of the national grid. It controlled the selected generators and provided a real time display of the time error between a reference standard and the 50 Hz mains frequency. The system comprised an HP 5280A reversible counter with two inputs, one from the mains 50 Hz as generated and one from the reference standard. These two inputs were arranged to add counts from one input and subtract counts from the other, such that the counter displayed zero while the generated 50 Hz was accurate. Offsets from 50Hz were displayed as positive or negative counts. The reference input was derived from an HP 105A quartz oscillator and the system included provision to manually synch that to the national standard time standard on an as required basis. The output of the 5280A counter drove an HP 6933B D/A converter, the bi-polar DC output of which was used (both magnitude and sign) to control the governors on some of the hydro generators. Dual HP 5321B clocks were used to display TOD from both sources. The 6933B is complete but the 5280A counter has been partly disassembled. The 5321Bs never got this far-neither did the 105A- who knows, it might still be being used as a reference! DaveB, NZ -Original Message- From: time-nuts [mailto:time-nuts-boun...@lists.febo.com] On Behalf Of Bill Hawkins Sent: Monday, July 08, 2019 06:48 To: Bob via time-nuts Subject: Re: [time-nuts] A Research Proposal Group, We've discussed this before, but maybe it needs to be said again. Line frequency is not constant. There is no master PLL. Approximate frequency is maintained by a central power dispatching office in each of the four (?) regions tied together by their power distribution grid. The dispatcher's goal is to create the same number of cycles of AC each day. IIRC, power is bought and sold by the number of cycles generated. As the daytime load increases, the generators slow down a bit. Note that it is not possible for each generating station to control its frequency, as that would not be stable. Instead, the dispatcher asks various plant operators to generate more or less steam (or water flow) in order to increase the frequency. When the load drops at night, the generators speed up a bit, and steam has to be reduced. At the end of the day, so to speak, the number of cycles generated is very nearly equal to the number generated if the line frequency had been steady at 60 (or 50) cycles per second. Synchronous clocks stay accurate although they may be off by a few seconds as dispatchers scramble to get enough steam to keep up. So yes, you can get phase data within a region but you must compensate timing data as the frequency varies. The regions are connected to each other for purposes of power sharing with DC transmission lines. These use inverters to convert between AC and
[time-nuts] Data collection sample interval and duration
I have been collecting data previously at a one second interval for a duration of 24 hours for my RFS. What are the potential "gotchas", if any, for a .1 second interval for say 6 hours? Will going to a shorter sample interval skew the results I have been seeing previously with the one second intervals? Thanks. ___ 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 Glen, You're welcome. Nothing wrong with the modules, I just like to well-document my hobbyprojects. I'm a bit crazy... Still some open ends that I would like to understand and update my drawings afterwards (and post the final versions). Maybe one of you guys knows how it's built, or maybe Rick K. can shed some light here... BR, Rob ___ 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] A Research Proposal
The message that the TrueTime/Symmetricom FTM-III power line monitor card for the XL/XLi receivers contains: A time error (number of accumulated seconds of error based upon the line frequency) The current frequency error from nominal 50/60 Hz The current measured line frequency (0.001 Hz res). The time that a line freq driven clock would be showing. ___ 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
To clarify: My research proposal is for data to be taken within the same interconnection. It does not care about frequency. It does not care about Time Error. It only seeks to characterize the phase differences between the power line signal presented in regions of the distribution system separated by significant geographical distances. 180-degree phase reversals and three-phase transformations along the chain of information are easily distinguishable. Thanks for your interest. I hope some will accept the technical challenge of gathering data -- which is fairly minimal. Andy Backus Bellingham, WA (Western Interconnection) From: time-nuts on behalf of Dave ZL3FJ <2c...@silverbears.nz> Sent: Sunday, July 7, 2019 9:23 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] A Research Proposal I have here a pair of instruments that were part of a system used at one time in a power station here in NZ to control the time error in one part of the national grid. It controlled the selected generators and provided a real time display of the time error between a reference standard and the 50 Hz mains frequency. The system comprised an HP 5280A reversible counter with two inputs, one from the mains 50 Hz as generated and one from the reference standard. These two inputs were arranged to add counts from one input and subtract counts from the other, such that the counter displayed zero while the generated 50 Hz was accurate. Offsets from 50Hz were displayed as positive or negative counts. The reference input was derived from an HP 105A quartz oscillator and the system included provision to manually synch that to the national standard time standard on an as required basis. The output of the 5280A counter drove an HP 6933B D/A converter, the bi-polar DC output of which was used (both magnitude and sign) to control the governors on some of the hydro generators. Dual HP 5321B clocks were used to display TOD from both sources. The 6933B is complete but the 5280A counter has been partly disassembled. The 5321Bs never got this far-neither did the 105A- who knows, it might still be being used as a reference! DaveB, NZ -Original Message- From: time-nuts [mailto:time-nuts-boun...@lists.febo.com] On Behalf Of Bill Hawkins Sent: Monday, July 08, 2019 06:48 To: Bob via time-nuts Subject: Re: [time-nuts] A Research Proposal Group, We've discussed this before, but maybe it needs to be said again. Line frequency is not constant. There is no master PLL. Approximate frequency is maintained by a central power dispatching office in each of the four (?) regions tied together by their power distribution grid. The dispatcher's goal is to create the same number of cycles of AC each day. IIRC, power is bought and sold by the number of cycles generated. As the daytime load increases, the generators slow down a bit. Note that it is not possible for each generating station to control its frequency, as that would not be stable. Instead, the dispatcher asks various plant operators to generate more or less steam (or water flow) in order to increase the frequency. When the load drops at night, the generators speed up a bit, and steam has to be reduced. At the end of the day, so to speak, the number of cycles generated is very nearly equal to the number generated if the line frequency had been steady at 60 (or 50) cycles per second. Synchronous clocks stay accurate although they may be off by a few seconds as dispatchers scramble to get enough steam to keep up. So yes, you can get phase data within a region but you must compensate timing data as the frequency varies. The regions are connected to each other for purposes of power sharing with DC transmission lines. These use inverters to convert between AC and DC. The AC frequency is controlled by the grid that it is tied to. Phase angle can be changed to change the amount and direction of the power transferred. So no, you can't compare data from different regions, unless you want to know which way DC power is flowing. I hope this was informative. Bill Hawkins On Thu, Jul 4, 2019, at 2:00 PM, Andy Backus wrote: > Historically, and even today, the steady frequency of AC power has > been used for timekeeping. So there may be interest here in the > following research proposal: > > Within a given power distribution grid, several observers as widely > separated geographically as possible, time stamp the first two zero > crossings of the power line after each UTC second – over the course of > 24 hours (86,400 pairs of data). > > Popularly conceived, all the components of a power distribution grid > are phase locked – though, of course, power is taken in and out by > varying degrees of lead or lag. Frequency is maintained by a constant > balancing act between load and generation. > > Typical power distribution grids, however, are sized on a scale
Re: [time-nuts] A Research Proposal
I have here a pair of instruments that were part of a system used at one time in a power station here in NZ to control the time error in one part of the national grid. It controlled the selected generators and provided a real time display of the time error between a reference standard and the 50 Hz mains frequency. The system comprised an HP 5280A reversible counter with two inputs, one from the mains 50 Hz as generated and one from the reference standard. These two inputs were arranged to add counts from one input and subtract counts from the other, such that the counter displayed zero while the generated 50 Hz was accurate. Offsets from 50Hz were displayed as positive or negative counts. The reference input was derived from an HP 105A quartz oscillator and the system included provision to manually synch that to the national standard time standard on an as required basis. The output of the 5280A counter drove an HP 6933B D/A converter, the bi-polar DC output of which was used (both magnitude and sign) to control the governors on some of the hydro generators. Dual HP 5321B clocks were used to display TOD from both sources. The 6933B is complete but the 5280A counter has been partly disassembled. The 5321Bs never got this far-neither did the 105A- who knows, it might still be being used as a reference! DaveB, NZ -Original Message- From: time-nuts [mailto:time-nuts-boun...@lists.febo.com] On Behalf Of Bill Hawkins Sent: Monday, July 08, 2019 06:48 To: Bob via time-nuts Subject: Re: [time-nuts] A Research Proposal Group, We've discussed this before, but maybe it needs to be said again. Line frequency is not constant. There is no master PLL. Approximate frequency is maintained by a central power dispatching office in each of the four (?) regions tied together by their power distribution grid. The dispatcher's goal is to create the same number of cycles of AC each day. IIRC, power is bought and sold by the number of cycles generated. As the daytime load increases, the generators slow down a bit. Note that it is not possible for each generating station to control its frequency, as that would not be stable. Instead, the dispatcher asks various plant operators to generate more or less steam (or water flow) in order to increase the frequency. When the load drops at night, the generators speed up a bit, and steam has to be reduced. At the end of the day, so to speak, the number of cycles generated is very nearly equal to the number generated if the line frequency had been steady at 60 (or 50) cycles per second. Synchronous clocks stay accurate although they may be off by a few seconds as dispatchers scramble to get enough steam to keep up. So yes, you can get phase data within a region but you must compensate timing data as the frequency varies. The regions are connected to each other for purposes of power sharing with DC transmission lines. These use inverters to convert between AC and DC. The AC frequency is controlled by the grid that it is tied to. Phase angle can be changed to change the amount and direction of the power transferred. So no, you can't compare data from different regions, unless you want to know which way DC power is flowing. I hope this was informative. Bill Hawkins On Thu, Jul 4, 2019, at 2:00 PM, Andy Backus wrote: > Historically, and even today, the steady frequency of AC power has > been used for timekeeping. So there may be interest here in the > following research proposal: > > Within a given power distribution grid, several observers as widely > separated geographically as possible, time stamp the first two zero > crossings of the power line after each UTC second – over the course of > 24 hours (86,400 pairs of data). > > Popularly conceived, all the components of a power distribution grid > are phase locked – though, of course, power is taken in and out by > varying degrees of lead or lag. Frequency is maintained by a constant > balancing act between load and generation. > > Typical power distribution grids, however, are sized on a scale of > thousands of miles. “Locking phase,” then, is problematic simply on > the basis of the limits of information transmission rate. Even at c, > every 1000 miles takes 5 ms, which represents a third to a quarter of > the period of the AC power waveform. > > Many interesting phenomena might result from that reality, which > suggests a certain constrained flexibility over large distances – > almost as if the system is like a large lake of viscous liquid. When > there are local disturbances such as rapid load changes or sudden > generation adjustments, for example, it is quite possible harmonic > ripples could be propagated through the system. > > Such effects could be observed by comparing phase data across > significant distances within a distribution grid. > > Andy Backus > Bellingham, WA > USA > > > From:
Re: [time-nuts] A Research Proposal
Since the direction of power flow depends on the phase angle between the synchronous source and load, it seems to me that the difference between the average phase angle in one region and that in another (at the ends of a DC transmission line) will tell you which way power is flowing. I didn't claim that the amount of power could be determined. It can't. Disclaimer - I'm a mechanical engineer who has made a career in the control of physical machines. I've been interested in the power line stuff since a visit to the PenJerDel region distribution control center in the seventies. Now that I'm 81, there's probably some holes in that knowledge. Bill Hawkins P.S. I don't know who Bob is. That's the address pobox gave me when I said "Reply to List" On Sun, Jul 7, 2019, at 5:00 PM, Hal Murray wrote: > > > So no, you can't compare data from different regions, unless you want to > > know > > which way DC power is flowing. > > How does knowing data about two regions tell me anything about how much power > is flowing and which direction? > > > > -- > 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.
