Re: [time-nuts] FLL errors
Ah, Magnus, source of so much solid and useful information, I don't see a time loop as valid. Frequency, yes, social time, no. A clock (purveyor of time) consists of an oscillator and a counter. In olden times the oscillator was a pendulum and the counter was a set of gears driven by the tick-tock of the escapement. Today we have electronic local oscillators providing one pulse per second (or whatever is needed) to electronic counters and displays. As an old timer, I prefer neon Nixie tubes. The problem we struggle to solve is to relate our local oscillator to some widely recognized standard frequency, preferably derived from an inordinately expensive generator based on the bouncing of atoms under controlled conditions. The very best way to transfer the standard (not At the tone, the time is ...) is to use an electronic phase comparator, error amplifier, and filter time constant that will cause the local oscillator to track the standard *frequency* usually propagated by GPS. The remaining problem is to get the counter to agree with our preferred version of time display (UTC, TAI, etc.). If the display electronics permit adjustments such as adding a second at a predetermined time, or adjusting by an hour for summer or winter time, then our needs for social time can be satisfied. I don't see the need to yank the oscillator around for social time with a time loop. Best regards, Bill Hawkins P.S. We're moving to a life care community that has no room for a time lab. The Junk Genius truck arrives at 10300 Colorado Road, Bloomington, MN 55438, at 11 AM on 1 September. If you can get here before that you can have anything you see. There are only antiques, except possibly the HP 3335A synthesizers and Racal Dana 1882 counters. I've tried to sell a few times but have had no takers. I won't ship (no time) but you can hire someone to pick it up. -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Saturday, August 29, 2015 9:47 PM To: Discussion of precise time and frequency measurement Cc: mag...@rubidium.se Subject: Re: [time-nuts] FLL errors Hi, On 08/29/2015 11:24 AM, Neville Michie wrote: A PLL locks on to the nearest cycle, is a Time Locked Loop different? Yes and now. In a signal conveying time, rather than letting a rising edge denote 0 degrees of phase you have some even time measure occuring, of some known nominal rate. You know what time it was on the time-scale, so that you know how much your local replica time-scale is off when compared. This time difference does go beyond the nearest cycle, but typically for locked situations is the nearest cycle. Don't ask how I know, I just know. If the decoded time from a GPS system is used discipline an oscillator then leap seconds would have to have a frequency transient to maintain lock. No, as GPS time in itself does not have leap-seconds, it's nominally the TAI time-scale offset. GPS signal conveys the difference between GPS time and UTC, and thuse the UTC can be conveyed. If you use the output to say drive a radio telescope monitoring a distant object you would want Earth's rotation to be phase or sidereal Time locked. I realise that for such a task far more complex computation would be required. So is a time locked loop a valid concept? Yes, whenever the enumeration of cycles to some time-scale is relevant. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP5065A C-field current is temperature sensitive
Hi Another counter argument against the “ratio mode” is that with zero current through the wiper, odd things can happen. There is *always* something else to consider in any real design. Since they needed to calibrate the voltage swing, there aren’t a lot of options with the technology they were using at the time. Today there are a lot more choices of how to get this sort of job done. Bob On Aug 30, 2015, at 8:05 AM, Adrian rfn...@arcor.de wrote: Bob, agreed. But in the 5065A C-field circuit, the pot is wired as a variable resistor. The Bourns data sheets specifies +/- 50 ppm / deg C max. Together with the two series resistors, the effective TC of the pot drops to about 20 ppm. That is indeed just 2 times more than the effective temperature coefficient of the reference diode (1N938). Btw. the 1N938 is running at about 7.5 mA +/- 1 mA, not at 12 mA as mentioned earlier. Some 3.5 to 5.5 mA are going through R8, R6, R12. To get the correct diode current, this current has to be subtractrd from the total current through R7 (Q5, Q6 base currents neglected). Adrian Bob Camp schrieb: Hi Most potentiometers have very good TC when used in a “ratio mode”. You can quickly mess that up by putting resistance in series with the pot. It’s a bit surprising how may times you see this inherent stability messed up that way. Bob On Aug 29, 2015, at 9:03 AM, Adrian rfn...@arcor.de wrote: Keep in mind that potentiometer R6 is one of the key components of the C-field circuit. Together with R8 and R12, it defines the reference voltage to Q6A/B. The tempco of that wire-wound potentiometer can certainly not be neglected. I would suggest to check the C-field temperature dependency with an external precision current source feeding the C-coil directly. Adrian Poul-Henning Kamp schrieb: Using the Fluke 732A as voltage reference improved HP5065A stability, but not very much, so I looked closer at the constant-current generator and the C-field pots calibration: http://phk.freebsd.dk/hacks/HP5065A/20150828_c_pot/index.html ... and found out that the current-sensing resistors R10||R11 have a very high temp-co. Getting closer... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] looking for SMT oscillator SC cut, with no oven
On 8/29/15 7:19 PM, Alex Pummer wrote: Hi Bob, go to your local city library get membership[ here in California it is free] , and ask them to get from the university library, it will take some time than they cal you the your stuff is there, you could have it for four weeks if you need you could extend it for an other four weeks, the engineering library of the university of Berkeley is open to everybody, you can not take it out without additional formality, but you could read, copy, scan it there, I assume that works similarly in your state/ city/ university library, If you have a specific title, let me know, it will not happen right away, since I am working on five projects [for clients] also I am [life] member of the IEEE, where is not everything free any more, but people are reasonable 73 As a Californian, I thought similarly.. all the UC libraries are open to the public and you can get free access to online resources (e.g. IEEE Xplore) via free public workstations; although printing stuff costs money. There might be visiting hour restrictions for the general public (no showing up at 3 AM), and most of them do require some kind of photo ID. However, a bit of casual browsing shows that this is decidedly NOT the case in other states. The Ohio State University, as far as I can tell, requires you to be a member of Friends of the Library, which is not free. It was unclear whether free access to Univ of Washington libraries includes online access (on-site). Fascinating. Local public libraries vary (even in California) on their interlibrary loan/ability to request copies of articles. It depends on local budgets and politics. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] Sphere's Stuff Day coming this friday, Sept. 5th!
We will have (literally) tons of free electronic parts and gear, plus some very interesting Time Nuts goodies, including an assortment of time code displays, counters, generators and converters left for just $25 ea. We even have some giant 4 foot wide time displays, make your own mission control site! There are also many Fluke, HP, Tek, GR, PMI/Wavetek, Boonton and other items, both free and for very low prices. There's at least 3 scalar analyzers, many microwave power meters, two noise sources, and freshly overhauled Fluke DMM's for just $39 with new leads. There's a pile of totally free new Chinese DMM's we bought, and just didn't like, it just re-affirms my opinion hat Fluke really does make the best handheld DMMs. Also a nice mix of high end counters, inexpensive scopes and some freshly cal'd HP 8656B's generators if anyone is interested. I also found a big pile of mint HP scope probes, for scopes to 250Mhz, with all the accessories, very hard to find. There's some Tek Logic Analyzer pod kits (new) still left, as well as some 7K plug ins, a 5K scope and misc. Tek spares and new boards that keep turning up in the strangest places. We have to remove EVERYTHING on the bottom floor to re-do the water damaged wood floor, so we are going to get rid of a lot of stuff to make this job a bit easier. ALSO, we have a big pile of generic, Tek and HP CRTs, we will put them out at just $25 each, but you *HAVE TO RSVP* and indicate *what you are interested in*, it's a lot of work and many trips to get them set out for the event. If no comments, we won't set them out. There will also be a lot of RF tubes and euro tubes for radio guys, and some RF wattmeters, lightning arrestors, amps and other goodies for the radio-amateurs. Also many PMI/Wavetek 1038 plug ins, hp 8660 series plug ins, and Argo Systems precision frequency generator plug ins (including a spare 10Mhz rubidium clock). We will put them out if we get feedback, otherwise no. They will go dirt cheap. Also a last minute addition, we have piles of *STK 100W low distortion audio amp modules* and new PCBs we made for them, just $10 for a set. Plus, some fantastic high performance speakers to make your own systems with, up to 6x9 with coaxial tweeters. High power resistor loads for amp testing too. Yes, we do take requests, if you are interested in something specific, PLEASE LET US KNOW in advance, there usually isn't much time at the event to look after those issues, and it is so much easier for everybody to arrange it in advance.. We are in British Columbia, right above Washington state, about 5 hours from Seattle. If you need navigation help or more info, please email or call Susan at the number below. The event will start at 8:30am saturday the 5th of Setember, until 4:30pm. We also have to open sunday afternoon for a few late travelers, so noon to 4:30pm on sunday the 6th. Hope to see you up here! We have people coming from BC, Alberta, Washington and Oregon, and everybody has a pretty good time here, so I encourage you to come up and snorkel around in the goodies. all the best, walter (walter2 -at- sphere.bc.ca) -- Walter Shawlee 2, President Sphere Research Corporation 3394 Sunnyside Rd., West Kelowna, BC V1Z 2V4 CANADA Phone: (250) 769-1834 walt...@sphere.bc.ca WS2: We're all in one boat, no matter how it looks to you. Love is all you need. (John Lennon) But, that doesn't mean other things don't come in handy. (WS2) ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Timepod Phase Noise Measurements and 3 corner hat
On Sunday, August 30, 2015 05:06:38 PM James Flynn wrote: Martyn Smith martyn@... writes: MEASUREMENT TECHNIQUE We have three sources close in frequency (within 1 x 10E-8 of each other). Two sources are connected to the Ch0 and Ch 2 inputs of the timepod, the unit under test to the ref input. According to John, the result will be the actual phase noise of the ref input, even if it is lower than the two other sources. No further calculations need to be made. The is a publication by the NPL that talks about a similar technique, but comes to a somewhat different conclusion. http://publications.npl.co.uk/npl_web/pdf/mgpg68.pdf Bottom line: it holds that the phase noise of all three sources can be determined if they are taken two at a time; one as ref and the other as the DUT. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. How can one have any faith in a paper that cant even get the fundamentals of resistor noise correct? It also perpetuates the myth that Ulrich Rodhe cofounded Rodhe and Schwarz. Lothar Rodhe (Ulrich's father I believe) cofounded Rodhe and Schwarz. Bruce ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP5065A C-field current is temperature sensitive
In message 1698d85b-ebb6-45e3-9cb0-cbf780ce5...@n1k.org, Bob Camp writes: Since they needed to calibrate the voltage swing, there aren’t a lot of options with the technology they were using at the time. Today there are a lot more choices of how to get this sort of job done. It's not just the swing, it's also the shape of the curve: http://phk.freebsd.dk/hacks/HP5065A/20150828_c_pot/index.html If it were just the range things would be a lot simpler. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why would Keysight UK uncertainty measuring 1 MHz be as high as 7.6 Hz?
Look at the service manual, the calibration setup listed is usually pretty close to what Keysight is using in their local calibration facility. For an LCR meter I doubt they would be using a time nuts grade counter Content by Scott Typos by Siri On Aug 29, 2015, at 10:02 PM, Bob Camp kb...@n1k.org wrote: Hi Well, since we all have made our totally uninformed guesses, the only thing to do now is to give Keysight a call and see what the real answer is. Bob On Aug 29, 2015, at 1:46 PM, Dr. David Kirkby (Kirkby Microwave Ltd) drkir...@kirkbymicrowave.co.uk wrote: On 29 August 2015 at 12:59, Javier Herrero jherr...@hvsistemas.es wrote: Hello, The calibration certificate does not indicate that the measurements were done with the frequency counters referenced to the 5071A at the time of calbiration (if so, it would be listed under the Calibration Equipment Used table). It says that the 53132A were calibrated against the 5071A. If for your calibration they have used 53132A witout the oven oscillator option it is very probable that its uncertainity is 7.6ppm as indicated in the certificate. Since the maximum error tolerable for the LCR meter is 100ppm (+/-100Hz @ 1MHz), it makes sense to perform the measurement with an instrument with an uncertainity of 7.6ppm, and not to use the better counter in the lab for that purpose. Regards, Javier I would find it a bit hard to believe they would use a counter without an oven in their lab, as it would seriously restrict what they can do with it, making it more difficult to replace one counter with another. I would have thought that within reason it best to have the lab have reasonably high spec kit, so more than one instrument could be done on the same line. They did for example use a pair of 3458As, despite I'm sure the voltage accuracy requirements could be met with a multimeter with far greater uncertainty than an expensive 3458A. It makes more sense (within reason) to have 3458As in the cal lab, as it allows a wider range of instruments to be calibrated. Also, if you consider the spec on the 53132A without an oven, it is 3 x 10^-7 per month. So after 12 months that could be 12 * 3 10^-7 or 3.6 10^-6, so if it did drift the maximum amount each month for a year, the uncertainty would higher than it actually is. I intended to contact Keysight about the calibration for a couple of other reasons 1) I would like to know if it was adjusted or not. That is not clear from the cal certificate, since the * As received condition - Not applicable, as this calibration certificate applies to the initial calibration of a new, refurbished or upgraded equipment. * Action taken - The equipment was upgraded. I doubt it has seen a cal lab in ages. The upgrade was just a software one, to enable cable lengths of 2 m and 4 m (option 006) to be used to connect the DUT, which they kindly provided free of charge, on the condition I paid for the calibration. 2) They never put any stickers over the screws that prevent the covers being removed, which struck me as a bit odd. Since I was going to ask about those two issues, I will ask about the uncertainty on frequency too. It will be interesting what response I get. I'm just interested - I realize that this instrument does not demand much of the counter used to calibrate it. The demanding calibration devices would be the resistance and capacitance standards. Dave ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP5065A C-field current is temperature sensitive
Bob, agreed. But in the 5065A C-field circuit, the pot is wired as a variable resistor. The Bourns data sheets specifies +/- 50 ppm / deg C max. Together with the two series resistors, the effective TC of the pot drops to about 20 ppm. That is indeed just 2 times more than the effective temperature coefficient of the reference diode (1N938). Btw. the 1N938 is running at about 7.5 mA +/- 1 mA, not at 12 mA as mentioned earlier. Some 3.5 to 5.5 mA are going through R8, R6, R12. To get the correct diode current, this current has to be subtractrd from the total current through R7 (Q5, Q6 base currents neglected). Adrian Bob Camp schrieb: Hi Most potentiometers have very good TC when used in a “ratio mode”. You can quickly mess that up by putting resistance in series with the pot. It’s a bit surprising how may times you see this inherent stability messed up that way. Bob On Aug 29, 2015, at 9:03 AM, Adrian rfn...@arcor.de wrote: Keep in mind that potentiometer R6 is one of the key components of the C-field circuit. Together with R8 and R12, it defines the reference voltage to Q6A/B. The tempco of that wire-wound potentiometer can certainly not be neglected. I would suggest to check the C-field temperature dependency with an external precision current source feeding the C-coil directly. Adrian Poul-Henning Kamp schrieb: Using the Fluke 732A as voltage reference improved HP5065A stability, but not very much, so I looked closer at the constant-current generator and the C-field pots calibration: http://phk.freebsd.dk/hacks/HP5065A/20150828_c_pot/index.html ... and found out that the current-sensing resistors R10||R11 have a very high temp-co. Getting closer... ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] FLL errors
Bill, On 08/30/2015 07:45 AM, Bill Hawkins wrote: Ah, Magnus, source of so much solid and useful information, I don't see a time loop as valid. Frequency, yes, social time, no. You say social time, but I didn't, you extrapolated my words. The main point of a Time Locked Loop is to use a enumeration beyond the cycles, so that you lock to the right cycle. This enumeration may be the code-phase of a GPS for instance. Some call this Delay Locked Loop while others call it a Time Locked Loop. You can also have a time-scale such as TAI or GPS time if you like, and there it makes sense. It's essentially a PLL, but aware of the enumeration so that the phase-detector has a much wider range such that false-lock cannot occur. Making the distinction from a normal PLL makes sense, and that's why both DLL and TLL is used. A clock (purveyor of time) consists of an oscillator and a counter. In olden times the oscillator was a pendulum and the counter was a set of gears driven by the tick-tock of the escapement. Today we have electronic local oscillators providing one pulse per second (or whatever is needed) to electronic counters and displays. As an old timer, I prefer neon Nixie tubes. The problem we struggle to solve is to relate our local oscillator to some widely recognized standard frequency, preferably derived from an inordinately expensive generator based on the bouncing of atoms under controlled conditions. The very best way to transfer the standard (not At the tone, the time is ...) is to use an electronic phase comparator, error amplifier, and filter time constant that will cause the local oscillator to track the standard *frequency* usually propagated by GPS. The remaining problem is to get the counter to agree with our preferred version of time display (UTC, TAI, etc.). If the display electronics permit adjustments such as adding a second at a predetermined time, or adjusting by an hour for summer or winter time, then our needs for social time can be satisfied. I don't see the need to yank the oscillator around for social time with a time loop. If you don't need it to, then don't do it. It doesn't mean others don't feel it being an adequate solution. I'm ot forcing anyone to any solution, I'm only want to show that there is cases where it does make sense to use one. Cheers, Magnus Best regards, Bill Hawkins P.S. We're moving to a life care community that has no room for a time lab. The Junk Genius truck arrives at 10300 Colorado Road, Bloomington, MN 55438, at 11 AM on 1 September. If you can get here before that you can have anything you see. There are only antiques, except possibly the HP 3335A synthesizers and Racal Dana 1882 counters. I've tried to sell a few times but have had no takers. I won't ship (no time) but you can hire someone to pick it up. -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Saturday, August 29, 2015 9:47 PM To: Discussion of precise time and frequency measurement Cc: mag...@rubidium.se Subject: Re: [time-nuts] FLL errors Hi, On 08/29/2015 11:24 AM, Neville Michie wrote: A PLL locks on to the nearest cycle, is a Time Locked Loop different? Yes and now. In a signal conveying time, rather than letting a rising edge denote 0 degrees of phase you have some even time measure occuring, of some known nominal rate. You know what time it was on the time-scale, so that you know how much your local replica time-scale is off when compared. This time difference does go beyond the nearest cycle, but typically for locked situations is the nearest cycle. Don't ask how I know, I just know. If the decoded time from a GPS system is used discipline an oscillator then leap seconds would have to have a frequency transient to maintain lock. No, as GPS time in itself does not have leap-seconds, it's nominally the TAI time-scale offset. GPS signal conveys the difference between GPS time and UTC, and thuse the UTC can be conveyed. If you use the output to say drive a radio telescope monitoring a distant object you would want Earth's rotation to be phase or sidereal Time locked. I realise that for such a task far more complex computation would be required. So is a time locked loop a valid concept? Yes, whenever the enumeration of cycles to some time-scale is relevant. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Timepod Phase Noise Measurements and 3 corner hat
The is a publication by the NPL that talks about a similar technique, but comes to a somewhat different conclusion. http://publications.npl.co.uk/npl_web/pdf/mgpg68.pdf Bottom line: it holds that the phase noise of all three sources can be determined if they are taken two at a time; one as ref and the other as the DUT. Yes, that's the three-cornered hat technique. The document is a bit dated in that respect -- it was published in 2004, just as Timing Solutions was starting to work on cross-correlated direct digital measurements. The dual-reference method always converges on the DUT noise if set up properly, but it doesn't give you any insight into the two independent sources being used as references. You have to swap the DUT with each of the references and repeat the measurement if you want to characterize all three sources, while the N-cornered hat returns separated variances for all sources at once (at least ideally.) -- john, KE5FX Miles Design LLC ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] KS-24361 REF-0 standalone
All, I hope some more of you have had luck getting your REF-0s running standalone. My earlier write-ups were focused on the bare minimum connections and code needed to make a REF-0 work. Of course, external connections are not ideal for long-term operations. The real end-state here is to have a nice board with a modern GPS that will install cleanly inside the REF-0. I have completed another write-up showing my work toward that goal. I show how you can access all of the necessary pins on the REF-0 directly on the board, without using the external Interface connector. I also show a simple prototype of my custom REF-0 GPS board. Here's the write-up: http://syncchannel.blogspot.com/2015/08/prototyping-gps-board-for-ks-24361-ref-0.html If you just want to solder something together, you can easily house your microcontroller and GPS on some protoboard as I did. This is the protoboard I used, it fits almost perfectly where a real Oncore GPS would go. I just had to widen the mounting holes with a drill. http://www.amazon.com/10Pcs-Double-Sided-Protoboard-Prototyping/dp/B00NQ387TY Beyond the prototype though, I personally want a nice PCB with a Ublox on it for my REF-0s. I plan to work on that as I have time. Though now that my summer break is over, time is a bit harder to find. :) Regards, Dan W. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP5065A C-field current is temperature sensitive
Hi As we go joyously bashing the poor guys that designed this beast, it’s worth noting just how old the design is. 741 op amps were indeed “modern” when they did much of this and quite possibly to modern to be trusted. Most of the design would have been right at home in the late 1960’s at a conservative design house. As time has shown, in a lot of cases that mistrust of the early linear stuff was well founded ….The 741 only was designed in 1968….The 5065 design dates to roughly that time. Bob On Aug 30, 2015, at 8:08 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: Poul-Henning, On 08/30/2015 09:54 PM, Poul-Henning Kamp wrote: In message 1698d85b-ebb6-45e3-9cb0-cbf780ce5...@n1k.org, Bob Camp writes: Since they needed to calibrate the voltage swing, there aren’t a lot of options with the technology they were using at the time. Today there are a lot more choices of how to get this sort of job done. It's not just the swing, it's also the shape of the curve: http://phk.freebsd.dk/hacks/HP5065A/20150828_c_pot/index.html If it were just the range things would be a lot simpler. Ehm, eh... that transistor pair you have there. How *tight* together is really the transistors thermal connection? I bet not all that good. The reason I got involved with counters and atomic references was originally my interest in analog synthesizers, and there we use a transistor pair for exponential conversion, which has scale and offset issues and thermal issues. The use of a Q81 +3300 ppm/C resistor in the division network helped to compensate the thermal properties of that transistor pair, and you wanted stuff like MAT-01 where the two transistors is thermally ties to each other and the put your tempco resistor to that for good performance. All this requires good measurement and good reference, so that what motivated me towards that step. Anyway, the take-away is that you should look at that discrete op-amp and see if it is not causing you the thermal dependence you are trying to locate. Maybe replace it with a more modern op-amp like the 741 or something (irony may have been used). Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP5065A C-field current is temperature sensitive
Poul-Henning, On 08/30/2015 09:54 PM, Poul-Henning Kamp wrote: In message 1698d85b-ebb6-45e3-9cb0-cbf780ce5...@n1k.org, Bob Camp writes: Since they needed to calibrate the voltage swing, there aren’t a lot of options with the technology they were using at the time. Today there are a lot more choices of how to get this sort of job done. It's not just the swing, it's also the shape of the curve: http://phk.freebsd.dk/hacks/HP5065A/20150828_c_pot/index.html If it were just the range things would be a lot simpler. Ehm, eh... that transistor pair you have there. How *tight* together is really the transistors thermal connection? I bet not all that good. The reason I got involved with counters and atomic references was originally my interest in analog synthesizers, and there we use a transistor pair for exponential conversion, which has scale and offset issues and thermal issues. The use of a Q81 +3300 ppm/C resistor in the division network helped to compensate the thermal properties of that transistor pair, and you wanted stuff like MAT-01 where the two transistors is thermally ties to each other and the put your tempco resistor to that for good performance. All this requires good measurement and good reference, so that what motivated me towards that step. Anyway, the take-away is that you should look at that discrete op-amp and see if it is not causing you the thermal dependence you are trying to locate. Maybe replace it with a more modern op-amp like the 741 or something (irony may have been used). Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Timepod Phase Noise Measurements and 3 corner hat
John, On 08/31/2015 12:37 AM, John Miles wrote: The is a publication by the NPL that talks about a similar technique, but comes to a somewhat different conclusion. http://publications.npl.co.uk/npl_web/pdf/mgpg68.pdf Bottom line: it holds that the phase noise of all three sources can be determined if they are taken two at a time; one as ref and the other as the DUT. Yes, that's the three-cornered hat technique. The document is a bit dated in that respect -- it was published in 2004, just as Timing Solutions was starting to work on cross-correlated direct digital measurements. The dual-reference method always converges on the DUT noise if set up properly, but it doesn't give you any insight into the two independent sources being used as references. You have to swap the DUT with each of the references and repeat the measurement if you want to characterize all three sources, while the N-cornered hat returns separated variances for all sources at once (at least ideally.) Indeed. On that note, did you look more closely on the NIST analysis of cross-correlation and a possible cancellation and thus overly optimistic results? Did it have any consequence on your code? What did you take away from it? Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Stanford Research 725
Hi Ulrich, On 08/30/2015 09:58 PM, KA2WEU--- via time-nuts wrote: This is the measured phase noise of the 10 MHz output. Not quite state of the art but stable frequency . Any other data of other oscillator available ? 73 de Ulrich For the fun of it I did a few quick and dirty measurements some time back, with plots like these: https://rubidium.dyndns.org/~magnus/time/timelab/OSA8600_HP5065A_OSA8600_20120618_1.png White-noise isn't spectacular on them, but 1/f^3 isn't too shabby. With some clean-up I should be able to do some more of these. 73 de Magnus SA0MAD ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] GPS TIMING SOLUTION CXR LARUS 545000-9
Hi, I got at auction three CXR LARUS 54500-9 chassis. They slots are empty – no cards included. The chassis have two GPSDO slots and 13 others ??? The back panel has: 1. Two TNC antenna connectors 2. Three BNC connectors a. 10 MHz b. 1 PPS c. IRIG-B 3. RJxx TCC/IP 4. A Jones terminal for 48 vdc and Battery The chassis are 12 x 12 x 18 and 20 lbs. If you have cards here is the deal. $ 20.00 plus shipping (each). Negotiable Contact me offline for more details. Bill br...@otelco.net --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Timepod Phase Noise Measurements and 3 corner hat
On that note, did you look more closely on the NIST analysis of cross-correlation and a possible cancellation and thus overly optimistic results? Did it have any consequence on your code? What did you take away from it? Yes, you can definitely get divots in the PN trace, especially in multiple-hour runs needed to reach very low noise levels. I've seen that on occasion when making measurements with independent downconverters. If the DUT signal experiences significant phase shift in one downconverter path relative to the other, I imagine that's a good way to provoke this behavior. Fortunately I haven't run into any instances of the worst-case scenario described in the Nelson paper, where the whole noise floor collapses without any exhibiting any other weird artifacts. The phenomenon is certainly worth keeping in mind but most people are not going to run into it, especially with the Ch0 and Ch2 jumpers in place. -- john, KE5FX Miles Design LLC ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Timepod Phase Noise Measurements and 3 corner hat
Hi John, On 08/31/2015 05:12 AM, John Miles wrote: On that note, did you look more closely on the NIST analysis of cross-correlation and a possible cancellation and thus overly optimistic results? Did it have any consequence on your code? What did you take away from it? Yes, you can definitely get divots in the PN trace, especially in multiple-hour runs needed to reach very low noise levels. I've seen that on occasion when making measurements with independent downconverters. If the DUT signal experiences significant phase shift in one downconverter path relative to the other, I imagine that's a good way to provoke this behavior. Fortunately I haven't run into any instances of the worst-case scenario described in the Nelson paper, where the whole noise floor collapses without any exhibiting any other weird artifacts. The phenomenon is certainly worth keeping in mind but most people are not going to run into it, especially with the Ch0 and Ch2 jumpers in place. I'm the kind of guy that keeps those jumpers off and feeding three signals, so that's why I am asking. :) Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] HP5065A C-field current is temperature sensitive
Bob, Indeed. No bashing of the designer, it is an OK design for its age and intended stability vs complexity. My point was that after the 702 design, many things happen and one thing they learned was to handle the thermal balance. Already the 741 had taken a number of these steps. The get-away might be that caring a bit about the thermal properties of the operational amplifier could be where we can improve the design. Cheers, Magnus On 08/31/2015 04:09 AM, Bob Camp wrote: Hi As we go joyously bashing the poor guys that designed this beast, it’s worth noting just how old the design is. 741 op amps were indeed “modern” when they did much of this and quite possibly to modern to be trusted. Most of the design would have been right at home in the late 1960’s at a conservative design house. As time has shown, in a lot of cases that mistrust of the early linear stuff was well founded ….The 741 only was designed in 1968….The 5065 design dates to roughly that time. Bob On Aug 30, 2015, at 8:08 PM, Magnus Danielson mag...@rubidium.dyndns.org wrote: Poul-Henning, On 08/30/2015 09:54 PM, Poul-Henning Kamp wrote: In message 1698d85b-ebb6-45e3-9cb0-cbf780ce5...@n1k.org, Bob Camp writes: Since they needed to calibrate the voltage swing, there aren’t a lot of options with the technology they were using at the time. Today there are a lot more choices of how to get this sort of job done. It's not just the swing, it's also the shape of the curve: http://phk.freebsd.dk/hacks/HP5065A/20150828_c_pot/index.html If it were just the range things would be a lot simpler. Ehm, eh... that transistor pair you have there. How *tight* together is really the transistors thermal connection? I bet not all that good. The reason I got involved with counters and atomic references was originally my interest in analog synthesizers, and there we use a transistor pair for exponential conversion, which has scale and offset issues and thermal issues. The use of a Q81 +3300 ppm/C resistor in the division network helped to compensate the thermal properties of that transistor pair, and you wanted stuff like MAT-01 where the two transistors is thermally ties to each other and the put your tempco resistor to that for good performance. All this requires good measurement and good reference, so that what motivated me towards that step. Anyway, the take-away is that you should look at that discrete op-amp and see if it is not causing you the thermal dependence you are trying to locate. Maybe replace it with a more modern op-amp like the 741 or something (irony may have been used). Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
