Re: [time-nuts] HP 8924C's on ebay
Jeff Mock said the following on 11/29/2007 01:32 AM: > There seem to be a bunch of HP8924C's up on ebay for about $1500. It's > intended function is for CDMA testing, but it seems to be a pretty > general RF communications tester. Even if you don't care about the CDMA > stuff, it's a 1GHz spectrum analyzer, RF signal generator that can be > used as a tracking generator and sweeper (I think), power meter, and a > few other features. > > Does anyone have any experience with this thing? Is it something useful > for the money or a boat anchor? It looks interesting but I'm not sure I > need another big heavy box... The ad claims it's a derivative of the HP 8920B, and it looks like it. Several of us here in Dayton have 8920A or B units, and they are a very nice general purpose service monitor. The spec analyzer was an option, but it has decent performance (as noted, no super-narrow RBWs) and there is a tracking generator -- I don't recall if that's a separate option, or automatic if the spec an is included. One thing that's nice is that if the span is less than 1.5 MHz, it can demodulate the center-frequency signal to audio. The RF gen will do AM or FM modulation, with internal or external input. There are a couple of AF generators so it can do dual tone testing. The receiver has frequency power meter, audio level meter, SINAD, FM deviation, AM modulation percentage, etc. Back 7 or 8 years ago, a loaded 8920B brought >$10K, but Lucent had hundreds of them that were dumped to the market and that depressed the prices a lot. I think these days an 8920B goes for maybe $3-4K, and the A for maybe $1K less. (The A model has a slower processor and somewhat lower specs, but the same functionality.) John ___ 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] Chronometer contest sponsored by IEEE Spectrum
IEEE Spectrum, the magazine of the Institute of Electrical and Electronic Engineers, is issuing a D-I-Y challenge that may be of interest to the members of this group. The goal is to build the most accurate possible digital clock for under $100, accuracy to be measured before disciplining with GPS, WWVB or other external aides. It is required that all parts be generally available; for instance, you can use an OCXO (by all means!) but only if it?s currently available on the open market. Display should be seven-segment LEDs?we?re looking for a usable appliance, not just a science project. Winner?s photo and project will be published on the magazine, its Web site, or both. Please send entries to: [EMAIL PROTECTED] Philip E. Ross Senior editor IEEE Spectrum Magazine ___ 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] HP 8924C's on ebay
> There seem to be a bunch of HP8924C's up on ebay for about $1500. Caveat emptor: I've had problems with that seller and IIRC others have, too. In my case, hee sold me an HP Rb without a physics package, agreed to honor the t&c, took it back but then took months to refund my money -- and only after threats of legal action. On the plus side, he does package instruments well. :-) -ch ___ 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] Chronometer contest sponsored by IEEE Spectrum
At 10:42 AM -0500 11/29/07, [EMAIL PROTECTED] wrote: >IEEE Spectrum, the magazine of the Institute of Electrical and Electronic >Engineers, is issuing a D-I-Y challenge that may be of interest to the >members of this group. The goal is to build the most accurate possible >digital clock for under $100, accuracy to be measured before disciplining >with GPS, WWVB or other external aides. It is required that all parts be >generally available; for instance, you can use an OCXO (by all means!) but >only if it?s currently available on the open market. Display should be >seven-segment LEDs?we?re looking for a usable appliance, not just a >science project. Winner?s photo and project will be published on the >magazine, its Web site, or both. Phillip, That sounds like a really fun DIY project. However, this group could spend 3 weeks debating what is and isn't OK to do. I hope there are more rules than that! Questions that came to mind are: Are single-source parts OK? Are surplus parts such as Ebay OCXOs OK? (That's an 'open market' to me!) Can we machine our own oven housings on the CNC milling machine in our garage? May we use the cesium beam clock in our basement to set the oscillator frequency? What temperature range will it be tested over? What time period will the drift be measured over? I think you get the idea. It might be more fun to require that an OCXO be designed and built by the DIY-er out of commercially available crystals and resistors. That way, it's an engineering challenge instead of a procurement challenge, since IEEE is about engineering. -- --David Forbes, Tucson, AZ http://www.cathodecorner.com/ ___ 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] Chronometer contest sponsored by IEEE Spectrum
On Thu, 29 Nov 2007, David Forbes wrote: > > It might be more fun to require that an OCXO be designed and built by > the DIY-er out of commercially available crystals and resistors. That > way, it's an engineering challenge instead of a procurement > challenge, since IEEE is about engineering. > -- I second David's suggestion! The only REAL challenge would be to design the circuitry. Otherwise this is just a "rack & stack" project which is not engineering. Regards, Jeffrey Pawlan Sr member IEEE; MTT & UFFC societies ___ 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] Chronometer contest sponsored by IEEE Spectrum
In message: <[EMAIL PROTECTED]> Jeffrey Pawlan <[EMAIL PROTECTED]> writes: : : : On Thu, 29 Nov 2007, David Forbes wrote: : > : > It might be more fun to require that an OCXO be designed and built by : > the DIY-er out of commercially available crystals and resistors. That : > way, it's an engineering challenge instead of a procurement : > challenge, since IEEE is about engineering. : > -- : : : I second David's suggestion! The only REAL challenge would be to design the : circuitry. Otherwise this is just a "rack & stack" project which is not : engineering. If it wasn't for the $100 price point, I have exactly this in my office right now: Our product displays the time on 7-segment LEDs. However, our cost is somewhat more than $100 since we have an OCXO, a TCXO, a GPS receiver, an ARM and an FPGA plus lots of sheet metal and slots in the back for distribution modules. Warner ___ 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] Prologix & 3478A
Chuck I've got a Prologix 3.12 and a 3478A; I've only ever used the former with John Ms. s/w and HP analysers. I'll happily test it with the 3478A if you give me some simple instructions for a simple XP user. regards Grant Making changes for the sake of making changes is probably a folly. The Prologix concept is sound the way it is, but it should have some mention of the known limitations. It would be nice if we could find a couple of other folks that have 3478's to test with the Prologix unit. Because the 3478 uses 75ALS160/161's, it could have the tristate/pullup modes selected by the microprocessor. So it could be a part failure, or a firmware problem. I will try and determine which is true, but it will have to wait for a while. Thanks to all for their help and input into my problem -Chuck Harris ___ 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] Chronometer contest sponsored by IEEE Spectrum
Jeffrey Pawlan wrote: > > On Thu, 29 Nov 2007, David Forbes wrote: >> It might be more fun to require that an OCXO be designed and built by >> the DIY-er out of commercially available crystals and resistors. That >> way, it's an engineering challenge instead of a procurement >> challenge, since IEEE is about engineering. >> -- > > I second David's suggestion! The only REAL challenge would be to design the > circuitry. Otherwise this is just a "rack & stack" project which is not > engineering. > I think it's a fantastic challenge. I imagine starting with a design goal something like tvb's original leapsecond goal. It would be kind of cool to have a $100 clock that met that criteria. I don't think an off-the shelf OCXO timebase will be competitive at this price point. I'm not aware of an inexpensive SC-cut oscillator. I think the parameters for the contest need to be tightened up. Temperature and environment are enemies for this kind of clock, I hope they specify the operating environment and time period for evaluation. I think that I would start by looking at 32kHz watch crystals, I've often wondered how good a timebase you can make out of one. The tempco is a parabola around 25C with a max slope of something like 0.05 PPM/C, so they are naturally a pretty good timebase with good aging characteristics. The crystals are really tiny, maybe insulating it with a material that has an interesting heat of fusion along with a micro to model the physics of the parabolic shape of the crystal performance. jeff ___ 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] Chronometer contest sponsored by IEEE Spectrum
David Forbes wrote: > At 10:42 AM -0500 11/29/07, [EMAIL PROTECTED] wrote: >> IEEE Spectrum, the magazine of the Institute of Electrical and Electronic >> Engineers, is issuing a D-I-Y challenge that may be of interest to the >> members of this group. The goal is to build the most accurate possible >> digital clock for under $100, accuracy to be measured before disciplining >> with GPS, WWVB or other external aides. It is required that all parts be >> generally available; for instance, you can use an OCXO (by all means!) but >> only if it?s currently available on the open market. Display should be >> seven-segment LEDs?we?re looking for a usable appliance, not just a >> science project. Winner?s photo and project will be published on the >> magazine, its Web site, or both. > > Phillip, > > That sounds like a really fun DIY project. However, this group could > spend 3 weeks debating what is and isn't OK to do. I hope there are > more rules than that! Building off of David's comment (and I know there have been some others since his...): Cool idea that it is, I think Spectrum needs to be really careful in how they define this contest. As David noted, the folks on this list are capable of arguing endlessly over extraordinarily fine details, and without carefully defining what "most accurate possible" means, more heat than light will be generated. Also, the requirement for LED displays is really inconsistent with the design goal; something that uses the eye as a measurement trigger is more limited by the interface than the resonator -- unless you're planning to measure the accuracy over a period of years. To get meaningful results, at a minimum you'll need to specify (a) the temperature range over which the clock has to operate, and (b) the time period over which the measurement will be taken. Allowing commercial OCXOs will take away most of the challenge, as that one element contributes almost all of the clock's frequency stability and accuracy. I think that requiring that the oscillator start with a discrete crystal (or other resonator), and that all temperature, voltage, and other environmental control mechanisms be designed and built by the submitter, would make for a really interesting competition that encompasses both electrical and mechanical design (and craftsmanship). John ___ 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] Chronometer contest sponsored by IEEE Spectrum
In message <[EMAIL PROTECTED]>, "M. Warner Losh" writes : >If it wasn't for the $100 price point, I have exactly this in my >office right now: Our product displays the time on 7-segment LEDs. >However, our cost is somewhat more than $100 since we have an OCXO, >a TCXO, a GPS receiver, an ARM and an FPGA plus lots of sheet metal >and slots in the back for distribution modules. Offer it at a suitable discount ? :-) -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 [EMAIL PROTECTED] | 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] Prologix & 3478A
Hi Grant, It is an axiom of the GPIB world that if a device gets addressed, it will sit up at attention and wait for commands. The 3478A shows that it is waiting by lighting up a couple of annunciators on the bottom row of the LCD that you never see otherwise. All you have to do to test whether the Prologix can work with your 3478A is address it. So, if you change the 3478A's address to match your HP analyzer's, and then run John's program, you should see these annunciators light up. The 3478A won't do anything useful that way, but it will prove that it hears the Prologix, something mine can't do. -Chuck Harris Grant Hodgson wrote: > Chuck > > I've got a Prologix 3.12 and a 3478A; I've only ever used the former > with John Ms. s/w and HP analysers. I'll happily test it with the 3478A > if you give me some simple instructions for a simple XP user. > > regards > > Grant ___ 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] Fluke 6681/Pendulum CNT-81 arrival
Hi! Today my Fluke 6681/Pendulum CNT-81 arrived, one of the ones that showed up on Ebay from Singapore a few weeks back. The calibration is still valid (but then, the internal memory of it was lost and no paper, ah well, like I really cared). It powered up nicely except for the comment that it lost the calibration memory, but that can be handled. It was a bit dirty, but some warm water and a cloth should handle that. No problem operating it. With 25 ps single-shot resolution it should be a nice counter for TI exercises. Wasting the CNT-90 on static measurements isn't that fun, and the CNT-81 isn't as noisy and powerhungry as the 5370B, which is a good thing most of the time. Hmm, I should make a counter test soon. Just awaiting the next counter... :-P 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] Of rubidium life and piggy-bank anemia....
Greetings, all-- As a newbie to this list, I am playing catchup in a number of arenas so please forgive me if I post something which is old news to most. In any event, something John Miles said pointed me towards investigating what it would take to cobble up something that would get me to the next higher level of frequency accuracy that exceeded my Trimble Thunderbolt. My primary purpose is to have the most (relatively) accurate 10MHz or 100MHz frequency reference to use in measurements above 2GHz but below 24GHz. Obviously, a somewhat anemic piggy-bank prohibits me from dropping several thousands of $$$ (choke) on a surplus cesium reference, so I am going to have to settle for rubidium. I see lots of rubidium oscillators come and go on eBay for several hundred $$. I started out to see what it would take to replace the OCXO in my T-bolt with a rubidium oscillator. One concern I had was paying $400 for a surplus rubidium oscillator and then discovering that it only had a year or two of life left in it. I stumbled across an interesting (but a tad dated) Air Force study titled: Observations on the Reliability of Rubidium Frequency Standards on Block II/IIA GPS Satellites It is found at: http://tycho.usno.navy.mil/ptti/1995/Vol%2027_10.pdf It may well turn out that after the tears dry following the realization that I probably cannot afford a tighter frequency reference than my T-bolt provides I will just have to resign myself to the E-12 of the T-Bolt and be happy... Your thoughts and comments are most welcome-- Mike Baker Micanopy, Florida - ___ 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] Digital clock competition
Philip, I am interested in your design challenge for an accurate digital clock, but although I've searched the IEEE Spectrum on-line magazine, I can find no mention of it. All I have is an email from you circulated through the TimeNuts group. It will be important to know the ground rules for the project. For example, what is the expected operating environment? What is the power budget? Need the display be 7-segment, and is any other technology permitted? Where, when and how is the calibration to be performed, and over what time period will accuracy be checked, and by what method? Most especially, we need to know what the definition of parts being 'generally available' means, and we need to know who decides how the cost of construction is defined. I published a $30 design using recycled parts capable of 10sec/year some two years ago - how would I know if it would it be eligible? Please send me detailed information, or tell me where I may find it. If it's not been clearly defined then the competition will not generate any serious interest. Regards, Murray Greenman Senior Engineer, Oscillator Engineering, RAKON ___ 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] Of rubidium life and piggy-bank anemia....
Hi Mike -- Most modern Rbs, and particularly the small telecom ones (which is what most of the <$500 ones are) have a quite long lamp life; I haven't heard of any of them failing because of lamp burnout. However, note that those Rbs tend to have only modest short term stability and phase noise. In fact, the Tbolt is likely to be significantly better in those regards than the Rb. So swapping out the OCXO for an Rb may not be the best move. But on the other hand, having a free-running Rb that you calibrate against the Tbolt (or some other reference) every so often isn't a bad idea; it gives you a source that's independent of external factors. John Michael Baker said the following on 11/29/2007 05:31 PM: > Greetings, all-- > > As a newbie to this list, I am playing catchup > in a number of arenas so please forgive me if > I post something which is old news to most. > > In any event, something John Miles said pointed > me towards investigating what it would take to > cobble up something that would get me to the next > higher level of frequency accuracy that exceeded my > Trimble Thunderbolt. My primary purpose is to have > the most (relatively) accurate 10MHz or 100MHz frequency > reference to use in measurements above 2GHz but > below 24GHz. Obviously, a somewhat anemic piggy-bank > prohibits me from dropping several thousands of $$$ (choke) > on a surplus cesium reference, so I am going to have to > settle for rubidium. I see lots of rubidium oscillators > come and go on eBay for several hundred $$. > > I started out to see what it would take to replace the > OCXO in my T-bolt with a rubidium oscillator. One > concern I had was paying $400 for a surplus rubidium > oscillator and then discovering that it only had a year > or two of life left in it. > > I stumbled across an interesting (but a tad dated) Air > Force study titled: > > Observations on the Reliability of Rubidium Frequency > Standards on Block II/IIA GPS Satellites > > It is found at: > > http://tycho.usno.navy.mil/ptti/1995/Vol%2027_10.pdf > > It may well turn out that after the tears dry following > the realization that I probably cannot afford a tighter > frequency reference than my T-bolt provides I will just > have to resign myself to the E-12 of the T-Bolt > and be happy... > > Your thoughts and comments are most welcome-- > > Mike Baker > Micanopy, Florida > - > > > > > ___ > 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] Fluke 6681/Pendulum CNT-81 arrival
In regards to the Fluke 6681 does anyone know where a calibration manual could be found? Jeff - Original Message - From: "Magnus Danielson" <[EMAIL PROTECTED]> To: Sent: Thursday, November 29, 2007 5:25 PM Subject: [time-nuts] Fluke 6681/Pendulum CNT-81 arrival > Hi! > > Today my Fluke 6681/Pendulum CNT-81 arrived, one of the ones that showed > up on > Ebay from Singapore a few weeks back. The calibration is still valid (but > then, > the internal memory of it was lost and no paper, ah well, like I really > cared). > > It powered up nicely except for the comment that it lost the calibration > memory, but that can be handled. > It was a bit dirty, but some warm water and a cloth should handle that. > > No problem operating it. > > With 25 ps single-shot resolution it should be a nice counter for TI > exercises. > Wasting the CNT-90 on static measurements isn't that fun, and the CNT-81 > isn't > as noisy and powerhungry as the 5370B, which is a good thing most of the > time. > > Hmm, I should make a counter test soon. Just awaiting the next counter... > :-P > > 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] Fluke 6681/Pendulum CNT-81 arrival
From: "jshank" <[EMAIL PROTECTED]> Subject: Re: [time-nuts] Fluke 6681/Pendulum CNT-81 arrival Date: Thu, 29 Nov 2007 18:28:53 -0500 Message-ID: <[EMAIL PROTECTED]> > In regards to the Fluke 6681 does anyone know where a calibration manual > could be found? Ebay. It arrived to me quicker than the counter. Fluke/Pendulum should carry them as well. 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] Of rubidium life and piggy-bank anemia....
John Ackermann N8UR wrote: > > But on the other hand, having a free-running Rb that you calibrate > against the Tbolt (or some other reference) every so often isn't a bad > idea; it gives you a source that's independent of external factors. > > John This was the road to hell for me :) I bought a Z3801A (moral equivalent to the Trimble Thunderbolt) back in 2000. I've happily used it as my house reference for both PPS and 10MHz for many years confident that I have a solid timebase. For the last several years I've been designing spectrometers for radio telescopes and it's been convenient and sometimes essential to have a timebase that's not too much worse than a modern radio telescope. I see the lock light, I make a few plots, and I get a warm feeling that I know what time it is. http://www.mock.com/gps I recently bought an Rb source for fun. Nominally I use it as the timebase for my frequency counter and run everything else off of the z3801a. Now I live in constant state of flux not really knowing what 10MHz is anymore. I need more clocks, my Rb source is amplifying my personality quirks. jeff ___ 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] Chronometer contest sponsored by IEEE Spectrum
Jeff Mock wrote: > Jeffrey Pawlan wrote: > >> On Thu, 29 Nov 2007, David Forbes wrote: >> >>> It might be more fun to require that an OCXO be designed and built by >>> the DIY-er out of commercially available crystals and resistors. That >>> way, it's an engineering challenge instead of a procurement >>> challenge, since IEEE is about engineering. >>> -- >>> >> I second David's suggestion! The only REAL challenge would be to design the >> circuitry. Otherwise this is just a "rack & stack" project which is not >> engineering. >> >> > > I think it's a fantastic challenge. I imagine starting with a design > goal something like tvb's original leapsecond goal. It would be kind of > cool to have a $100 clock that met that criteria. > > I don't think an off-the shelf OCXO timebase will be competitive at this > price point. I'm not aware of an inexpensive SC-cut oscillator. > > I think the parameters for the contest need to be tightened up. > Temperature and environment are enemies for this kind of clock, I hope > they specify the operating environment and time period for evaluation. > > I think that I would start by looking at 32kHz watch crystals, I've > often wondered how good a timebase you can make out of one. The tempco > is a parabola around 25C with a max slope of something like 0.05 PPM/C, > so they are naturally a pretty good timebase with good aging > characteristics. The crystals are really tiny, maybe insulating it with > a material that has an interesting heat of fusion along with a micro to > model the physics of the parabolic shape of the crystal performance. > > jeff > > Maybe an ensemble of watch crystal clocks and a PIC microprocessor per David Allan paper of some years ago. After testing you could assign deferent weighting to the different clocks. Bill K7NOM ___ 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] 1Mhz to 1 PPS
At 06:02 AM 11/27/2007, you wrote: >You will need a clock shaper to convert the sine to a digital signal, and >a series of dividers. > >You can look at my page on clock shapers for ideas: > >http://www.ko4bb.com/Timing/ClockShaper.html > >If you look through the archives, I believe earlier this year there was a >thread about the respective noise performance of various logic >technologies, but I am sure someone can recommend the current >best-in-class divider for low noise. For any but the most demanding >applications, I am sure that standard CMOS decade counters in the AC, HC, >ACT or HCT series would work fine, such as the 74ACT162. While designing a timing distribution system at a cyclotron facility that required stability and low jitter (in the low picoseconds), I found that thermal changes caused the logic thresholds to vary which caused the edges to drift dozens of picoseconds. The solution was, whenever possible, to use differential logic signals. I was using the ECLips ECL logic family so that was an easy fix. Resync'ing to the input clock should be done as required and again close to the output. -Mike- ___ 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] Chronometer contest sponsored by IEEE Spectrum
>> I think that I would start by looking at 32kHz watch crystals, I've >> often wondered how good a timebase you can make out of one. The tempco >> is a parabola around 25C with a max slope of something like 0.05 PPM/C, >> so they are naturally a pretty good timebase with good aging >> characteristics. The crystals are really tiny, maybe insulating it with >> a material that has an interesting heat of fusion along with a micro to >> model the physics of the parabolic shape of the crystal performance. >> >> jeff >> >> > Maybe an ensemble of watch crystal clocks and a PIC microprocessor per > David Allan paper > of some years ago. After testing you could assign deferent weighting to > the different clocks. > > Bill K7NOM > Yes, an ensemble of 32kHz crystals, I like it a lot. Perhaps you can setup a temperature gradient from hot to cold across a number of crystals. If the tempco for the crystal is really a parabola, each of the crystals can be a datapoint along the parabola of crystal performance. With a little work you might be able to precisely calculate the maxima of the parabola and precisely set the frequency independent of temp and aging. Ha! jeff ___ 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] Of rubidium life and piggy-bank anemia....
A very old saying: Give a man a watch and he will always know what time it is. Give him two, and he is never sure. -Chuck Harris > This was the road to hell for me :) I bought a Z3801A (moral equivalent > to the Trimble Thunderbolt) back in 2000. I've happily used it as my > house reference for both PPS and 10MHz for many years confident that I > have a solid timebase. > > For the last several years I've been designing spectrometers for radio > telescopes and it's been convenient and sometimes essential to have a > timebase that's not too much worse than a modern radio telescope. I see > the lock light, I make a few plots, and I get a warm feeling that I know > what time it is. > http://www.mock.com/gps > > I recently bought an Rb source for fun. Nominally I use it as the > timebase for my frequency counter and run everything else off of the > z3801a. Now I live in constant state of flux not really knowing what > 10MHz is anymore. I need more clocks, my Rb source is amplifying my > personality quirks. > > jeff > > > ___ > 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] Of rubidium life and piggy-bank anemia....
So, is it a case where someone who has a Thunderbolt and a telco grade Rb should use the TB for normal use when GPS is up and use it to resync the Rb on occasion, so that the Rb can be used as a backup when the GPS goes out? Should the Rb be phase locked to the TB with a very long time constant, and if so, how long? I guess the answer is: plot the Allan Variance of the Rb, knowing what that of the TB is, and you know the answer :-) The problem is, if you only have a TB and an Rb, how do you plot the Allan Variance? Borrow tvb's Cesium? In favor of the TB, I may point out that the power consumption of a Rb oscillator is not negligible, compared to that of most GPSDOs. If you are concerned about heat or power consumption, you may want to consider that. Didier KO4BB > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of John Ackermann N8UR > Sent: Thursday, November 29, 2007 5:10 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Of rubidium life and piggy-bank anemia > > Hi Mike -- > > Most modern Rbs, and particularly the small telecom ones > (which is what most of the <$500 ones are) have a quite long > lamp life; I haven't heard of any of them failing because of > lamp burnout. > > However, note that those Rbs tend to have only modest short > term stability and phase noise. In fact, the Tbolt is likely > to be significantly better in those regards than the Rb. So > swapping out the OCXO for an Rb may not be the best move. > > But on the other hand, having a free-running Rb that you > calibrate against the Tbolt (or some other reference) every > so often isn't a bad idea; it gives you a source that's > independent of external factors. > > John ___ 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] Of rubidium life and piggy-bank anemia....
Hal Murray wrote: >> I think the rest of the saying probably is: "Give him three clocks, >> and he will start to calculate Allen Variances..." >> > > If I had a good clock (aka place to stand), I think I could use it to > calculate the Allen Variance of a not-so-good clock. > > How do I do it if I have several clocks and there isn't one that is obviously > better than the others? > > > Use the three cornered hat technique. 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] Chronometer contest sponsored by IEEE Spectrum
> Are surplus parts such as Ebay OCXOs OK? (That's an 'open market' to me!) I got eight 3 MHz OXCOs for $32. They don't have electric tuning, but the one I played with seems pretty stable. It takes a significant dip if I grab the can with my fingers but there isn't any obvious 24 hour pattern. Maybe there should be several categories: Sync to WWVB Sync to 60 Hz from the wall. Sync to GPS (you can get USB GPS units well under $100) Watch crystal - 32 KHz Other crystal Good local osc (TCXO, OCXO, ...) External frequency source - focus on display Say 10 MHz coax with power over the coax. Longest battery life (lowest power) Best accuracy per dollar measured over a month using Digikey's one-off pricing (or any major supplier) Coolest as determined by judge's whimsy. Any other categories the judges think appropriate. Built out of stuff in your junk box Only "junk" allowed Cesium OK if you already have one :) > Display should be seven-segment LEDs That seems like a strange restriction. It cuts out a lot of innovation that could be done on the display. It also mostly eliminates the battery powered area. Using the eye-ball to measure goodness of a clock seems like the wrong approach. How about adding a PPS test point to the requirements? > we're looking for a usable appliance, not just a science project. What's wrong with science projects? DIY stuff is inherently a project. Sometimes it's science, sometimes art, sometimes engineering, sometimes just fun. -- These are my opinions, not necessarily my employer's. I hate spam. ___ 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] Of rubidium life and piggy-bank anemia....
I think the rest of the saying probably is: "Give him three clocks, and he will start to calculate Allen Variances..." -Chuck Harris [EMAIL PROTECTED] wrote: > But TVB has added: > "That three clocks are better than two.so measure, measure, measure!" > > Or some words to that point. > > -Brian, WA1ZMS > > -Original Message- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > Behalf Of Chuck Harris > Sent: Thursday, November 29, 2007 9:35 PM > To: Discussion of precise time and frequency measurement > Subject: Re: [time-nuts] Of rubidium life and piggy-bank anemia > > > A very old saying: > > Give a man a watch and he will always know what time it is. Give > him two, and he is never sure. > > -Chuck Harris ___ 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] Of rubidium life and piggy-bank anemia....
> I think the rest of the saying probably is: "Give him three clocks, > and he will start to calculate Allen Variances..." If I had a good clock (aka place to stand), I think I could use it to calculate the Allen Variance of a not-so-good clock. How do I do it if I have several clocks and there isn't one that is obviously better than the others? -- These are my opinions, not necessarily my employer's. I hate spam. ___ 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] Digital clock competition
Personally, I think the choice of LED display for such a project is a poor one. You can get LCD displays for less than $15 if you look a little bit, and the power consumption will be much lower, which will make a number of other things easier and the end product more desirable, such as being able to run on batteries, which would be well aligned with modern trends. For such a project, it seems that a TCXO approach makes more sense than an OCXO. The XO and its temperature compensation could be precalibrated against a known good reference, and the end product would be stable and have low power consumption. A simple microcontroller would divide the crystal, drive the LCD, and do the temperature compensation. When is the due date for the project submissions? Didier KO4BB > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Murray Greenman > Sent: Thursday, November 29, 2007 4:58 PM > To: [EMAIL PROTECTED] > Cc: time-nuts@febo.com > Subject: [time-nuts] Digital clock competition > > Philip, > > I am interested in your design challenge for an accurate > digital clock, but although I've searched the IEEE Spectrum > on-line magazine, I can find no mention of it. All I have is > an email from you circulated through the TimeNuts group. > > It will be important to know the ground rules for the > project. For example, what is the expected operating > environment? What is the power budget? Need the display be > 7-segment, and is any other technology permitted? Where, when > and how is the calibration to be performed, and over what > time period will accuracy be checked, and by what method? > > Most especially, we need to know what the definition of parts > being 'generally available' means, and we need to know who > decides how the cost of construction is defined. I published > a $30 design using recycled parts capable of 10sec/year some > two years ago - how would I know if it would it be eligible? > > Please send me detailed information, or tell me where I may > find it. If it's not been clearly defined then the > competition will not generate any serious interest. > > Regards, > > Murray Greenman > Senior Engineer, > Oscillator Engineering, > RAKON > > ___ > 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] Of rubidium life and piggy-bank anemia....
But TVB has added: "That three clocks are better than two.so measure, measure, measure!" Or some words to that point. -Brian, WA1ZMS -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Chuck Harris Sent: Thursday, November 29, 2007 9:35 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Of rubidium life and piggy-bank anemia A very old saying: Give a man a watch and he will always know what time it is. Give him two, and he is never sure. -Chuck Harris > This was the road to hell for me :) I bought a Z3801A (moral equivalent > to the Trimble Thunderbolt) back in 2000. I've happily used it as my > house reference for both PPS and 10MHz for many years confident that I > have a solid timebase. > > For the last several years I've been designing spectrometers for radio > telescopes and it's been convenient and sometimes essential to have a > timebase that's not too much worse than a modern radio telescope. I see > the lock light, I make a few plots, and I get a warm feeling that I know > what time it is. > http://www.mock.com/gps > > I recently bought an Rb source for fun. Nominally I use it as the > timebase for my frequency counter and run everything else off of the > z3801a. Now I live in constant state of flux not really knowing what > 10MHz is anymore. I need more clocks, my Rb source is amplifying my > personality quirks. > > jeff > > > ___ > 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] Looking for HP5359A manual
Gentlemen, I just managed to buy an HP5359A time synthesizer on ebay. Has anyone of you a manual for that device in electronic form available that he can share with me? My search at the usual places (Agilent, Didier's pages, Boat anchor manuals) have not led to any result yet. Best regards Ulrich Bangert www.ulrich-bangert.de Ortholzer Weg 1 27243 Gross Ippener ___ 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.
