Re: [time-nuts] advice
Hi Bob and Rhoderick, I believe the experiment you're talking about is MINOS. If there are any specific questions regarding this, I can probe around. I work (indirectly) with a professor and his group that is a collaborator with MINOS and FermiLab. When I have some free time I will ask him about it; seems like something I would be interested in too. Ray Xu (more of an engineer, but a "physicist-in-training") On Tue, Feb 21, 2017 at 1:48 PM, Bob Stewart <b...@evoria.net> wrote: > Hi, > Have you been in touch with Fermi-Lab? They run a neutrino experiment > with a receiver somewhere underground in Wisconsin. At least that's what I > recall. I used to live next to a Physics professor who has a minor part in > the experiment. I'm not even sure what sort of data they collect there; > whether it's time or something else. > > Bob Stewart (Not a physicist) > > > From: Rhoderick Beery <rjbe...@gmail.com> > To: time-nuts@febo.com > Sent: Tuesday, February 21, 2017 11:13 AM > Subject: [time-nuts] advice > > Greetings Time-Nuts! > > I'm a physics theorist interested in performing an experiment to measure > the gravitational time dilation beneath the surface of the Earth. Boulby > Labs in the UK is 1.1 km down which would generate a time differential from > the surface on the order of 1 part in 10^15 -- not much to work with! > > I've investigated measuring redshift/blueshift from lasers but our > wavemeter technology is no where near accurate enough. I've concluded that > my best solution is to use atomic clocks, of which I know very little > about. I thought a clock-enthusiast mail group would be a fantastic way for > me to learn about the subject as well as possibly spur ideas on the lab > test design itself. > > Thanks in advance!! > --- > Rhoderick Beery > direct: 402-817-9363 > ___ > 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] modern electronics education/jobs (was:
Hi guys, Your mostly-lurking EE (and, recently, also physics) undergraduate student here. You guys make me feel nostalgic for my young age of almost-legal-to-drink-in-the-US! I wish I can reply to all of you one by one but I'd rather not clog the mailing list with more off-topic discussion. (Feel free to email me off-list) I just have to say I have a deep appreciation for the previous generation of electronics and technology and engineers (you guys). I personally feel like I've been born into the wrong generation, or at least "conflicted" between the two generations of electronics. I still enjoy hands-on DIY-building, soldering, dead-bug style prototyping, and etc at home but it definitely is starting to become obsolete and antiquated. On the other hand, I also enjoy working in research labs with the cutting-edge. In the former, time slows down and its just a matter of mostly applying knowledge. In the latter, time passes by quickly and its all about intellectual growth. When I was younger, I frequently interacted with engineers that used to be involved in the defense industry during the Cold War/Viet/Korean War era. They are now mostly retired. They were my main source of knowledge, and as a consequence, I grew up learning analog electronics by actual breadboarding, hand-soldering, playing with oscilloscopes, and reading The Art Of Electronics during my free time. It wasn't until relatively recently I started using LTSpice. I have never touched an Arduino or Raspberry Pi and I probably never want to*; I learned microcontrollers on my own using the PIC platform and in a few of my courses on the ARM and "LC3" platform. Perhaps the biggest contributor towards my passion and desire to learn about electronics is my family. My father bought me a brand new Tek oscilloscope during ~7th grade and made it clear to me that he will spend money for my hobby if it meant I will have the opportunity to learn. (This was significant, because from where I grew up, the Asian parents were stereotypically notorious for being frugal and only cared what their son's/daughter's GPA and test scores were) In the research (the "cutting-edge") world, I actually find my past and DIY experience useful in gaining an intuitive understanding of a problem or design challenge at hand. In the classroom, I heavily agree that most of my peers need more hands-on experience. Seriously, some people still can't explain why knowing the power dissipation of a resistor is important. Or how much current is flowing through a pull-low or pull-high bias resistor. Or what happens when you have a simple RC circuit (without having to write a transfer function). It's kind of disturbing. Maybe after I've obtained my PhD, I'd like to propose serious changes to the undergraduate EE curriculum of my university. Keep it up guys. If any of you are in the Austin, TX or Dallas, TX area, I am willing to meet up in person. On Thu, Nov 12, 2015 at 8:14 PM, Richard (Rick) Karlquist < rich...@karlquist.com> wrote: > > > On 11/12/2015 1:01 PM, William Schrempp wrote: > >> >> has failed. I hear old machinists complaining about new machinists who >> can't >> drill a hole if the drill-press isn't computer-controlled. And in my work, >> nurse education, I see students who can't be bothered to learn how to >> take a >> manual blood-pressure, because a machine can now do it (sort of). Much to >> ponder here. . . . >> > > Bill Schrempp >> >> > This reminds me of a summer job I had as a lab assistant between my > freshman and sophomore years at college. There were a couple of > journeyman machinists with Bridgeport mills. They didn't let me > use them, but they did patiently teach me how to use the drill > press, taps, hacksaw, etc to make simple parts that didn't require > their skills. They told me that, in Germany, a kid training to be > a machinist would start out by being given a file, a pair of calipers, > and a rough block of metal. His task was to make a perfect cube with > sides of exactly 1 cm by 1 cm. Only after mastering that, would > he be allowed to move onto more advanced equipment. Fortunately, the > machinists just told me this story to scare me, but they didn't make me > file a perfect cube. They did tell me I needed to learn to drill holes > with 0.005 inch accuracy using a machinist's scale and a center > punch to lay them out. > > Rick > > ___ > 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. > -- -- __ Ray Xu http://www.utdallas.edu/~rxx110130 ___ 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] Documents
Hi, Did you receive the Documents which I have sent earlier? If not, I have re-uploaded them on my Google drive. Click Here https://googledrive.com/host/0B6EMS-qB9qNxUXFWOFlXUUJHRU0, I will upload rest of the documents soon. Regards -- -- __ Ray Xu http://www.utdallas.edu/~rxx110130 ___ 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] science projects
Hi Jim Thank you for your reply, especially for your input on how science fair is judged. I've saved your reply and I'll be sure to read over it again before regional competition in a few weeks! No I have not done any research into Peter Siegel's work...Thanks for pointing that out to me. Speaking of IEEE, I should start reading over the stuff on there since I now have access to it through UTD... Thanks Ray Xu On Wed, Feb 8, 2012 at 10:23 PM, Jim Lux jim...@earthlink.net wrote: On 2/8/12 7:37 PM, Ray Xu wrote: Hi guys My 2 cents...from first person experience ;-) (although this doesn't have much to do with frequency standard-related science fair projects...) I am actually a high school junior in one of Dallas/Ft Worth, Texas's, suburbs, and I have been competing in ISEF science fairs for the last 3 years. From my experience, the engineering judges look for projects that are novel and can justify why this new method is better than mainstream methods. You bet. I *am* an ISEF engineering judge, and you are exactly right. You need to know your field well enough to be able to explain why what you are doing is different, and why there's at least a chance of it being better. Besides that, it is almost like a marketing fair since the presentation style also plays a huge role. In my opinion, high school ISEF science fair these days is not about hey look at what I made, but its more like how can it be done better and why should it replace mainstream technology. At the top levels, it has never been look what I made (the perjorative term is baking soda volcano). I don't know that presentation style is super important, at least at ISEF: there are entries from all around the world, from places with all manner of cultural styles and technical display proficiency. Most notably, a lot of the entrants aren't speaking English and are using a translator of variable quality (i.e. they may be able to translate Urdu and English, but odds are, they aren't an engineer) What the judges look for is - good explanation of what you did and why you did it - getting back to the idea of picking a good topic that's novel (where time-nuts can help, eh? research on background doesn't have to all be literature searches.. asking experts is good) - responding to questions as asked - We all get trained (or have experience and share notes) on stopping the elevator pitch - being able to answer obscure details about what you did (to root out the third assistant bottle washer in professor so-and-so's lab and the kit builder) - it being YOUR project (again, working as a team member in a university lab isn't going to be a winner for the fair.. good in real life, not good for competition) My project last year was essentially building a general purpose compact X-band radar system capable of distance and speed measurements. My major application was its use as no-physical-contact biomedical instruments. I got 2nd place at regionals and didnt advance any farther than state. In retrospect, I believe my weaknesses back then were because radars are nothing new; I just presented a new application and I feel like I could've presented my project better towards the judges. Yes.. you basically built a measurement instrument that already existed. If that had been incidental to your application, and you focused on the novelty of the application (e.g. detecting sleep apnea or something like that) it might have done better. Or, if your radar was somehow novel in design (e.g. you didn't use a gunnplexer or DRO based door opening radar as the base, and it wasn't a simple FMCW homodyne) I believe the live demo of a part of the radar, showing how professionally made it was (custom PCBs, etc), and the detailed documentation binder were a huge plus to my project. Yes and no. live demo is always good (because it shows YOU did it), and face it, it's SHOWTIME detailed documentation is good (shows good work practice, and if the judge picks a page at random and asks about it, and you can answer. I've judged software projects and done this, and the person had ZERO clue about what the module I was doing did and why it was there.) Professionally made, maybe, maybe not. Depends on the context and what resources you had available to you. I saw an amazing project last year that was literally built from scrap electronics the guys had scrounged at the junkyard in their third world country. I've never seen so many different kinds of connectors and ancient phenolic PC boards repurposed in my life. But the darn thing worked and did what they wanted. They got good marks on ingenuity and use of resources. (Their project topic wasn't all that great, unfortunately..) If you are living in Silicon Valley, and you show up with homemade PC boards or deadbug style construction, and you explained why that was the choice you made, rather than sending it out to any
Re: [time-nuts] science projects
Hi guys My 2 cents...from first person experience ;-) (although this doesn't have much to do with frequency standard-related science fair projects...) I am actually a high school junior in one of Dallas/Ft Worth, Texas's, suburbs, and I have been competing in ISEF science fairs for the last 3 years. From my experience, the engineering judges look for projects that are novel and can justify why this new method is better than mainstream methods. Besides that, it is almost like a marketing fair since the presentation style also plays a huge role. In my opinion, high school ISEF science fair these days is not about hey look at what I made, but its more like how can it be done better and why should it replace mainstream technology. My project last year was essentially building a general purpose compact X-band radar system capable of distance and speed measurements. My major application was its use as no-physical-contact biomedical instruments. I got 2nd place at regionals and didnt advance any farther than state. In retrospect, I believe my weaknesses back then were because radars are nothing new; I just presented a new application and I feel like I could've presented my project better towards the judges. I believe the live demo of a part of the radar, showing how professionally made it was (custom PCBs, etc), and the detailed documentation binder were a huge plus to my project. This year, I'm working on making a monolithic CMOS THz imaging array with built-in signal processing integrated circuit. (Just in case you're wondering, my I'm employeed at the TxACE center at UTD as a intern). My job is to basically design on the transistor level and integrate the signal processing circuit into the CMOS THz imaging array. At the end, I plan to use this project and compete in STS, Siemens, and ISEF. Unlike my last year's project, monolithic THz imaging arrays with on-chip signal processing is something relatively new. Why is a teenager (me) doing on this list? Because I have a passion for electronics, especially analog and RF ever since when I was very young. I love what I'm doing and I dont plan on stopping. Ok I'll stop rambling now...sorry for the long email guys... Ray Xu KF5LJO On Wed, Feb 8, 2012 at 8:03 PM, Chris Albertson albertson.ch...@gmail.comwrote: The number one TN science fair project would have to be measuring the speed of light using some simple, inexpensive method such as reflecting sunlight from rotating mirrors On Wed, Feb 8, 2012 at 5:44 PM, Jim Lux jim...@earthlink.net wrote: While delayed, I would think that the signal freqs would still need to be maintained... hmmm, maybe not... interesting science project... anyone? anyone? ;-) Jerry I'm waiting to see a good time-nuts project at the science fair. (at any level up to ISEF) There's a lot of good ones out there (perhaps not on the scale of tvb's experimental demonstration of gravitational effects on atomic clocks) that would lend themselves to execution by everyone from 6th to 12th grade. Clearly, since people do spend their entire professional life doing this and write dissertations on it, it can be up to ISEF or Siemens Talent Search standards. Maybe we could come up with a suggested list and start shopping it around. Jim ___ 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. -- Chris Albertson Redondo Beach, California ___ 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. -- __ 73, Ray Xu KF5LJO ___ 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] TM 5680-0211 for 5680A series Rubidiums
Same here, rayxu...@gmail.com Thank you Ray Xu On Tue, Jan 31, 2012 at 7:59 PM, Chris Albertson albertson.ch...@gmail.comwrote: On 31/01/12 22:14, Rob Kimberley wrote: If anyone is interested, I have just got hold of a PDF of the Technical Manual TM 5680-0211 for 5680A series Rubidiums. Please contact me off list for a copy (1M, so too large to post on time-nuts@febo.com) I'd ask off line but the quotes did not preserve your email address. Would you send a copy to me at albertson.ch...@gmail.com If you like, I can put this some place where others can get get directly Chris Albertson Redondo Beach, California ___ 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. -- __ 73, Ray Xu KF5LJO ___ 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] Building a GPSDO trouble using Jupiter-T
Hi Tom, I am just curious... What did you mean if the GPS was warmed up? Do you mean the Jupiter GPS unit its self to be warmed up? (if so, what does the Jupiter unit have to do with the oscillator stability, besides providing that 10KHz signal?) Great info, thanks. Do you have any documentation you could send me or website documenting your project? (hopefully I am not asking for too much! :-) ) Thanks On Sun, Jan 29, 2012 at 1:36 AM, Tom Curlee tcur...@sbcglobal.net wrote: Ray: I used a similar circuit to lock my 10 GHz LO to GPS. I used a similar Jupiter GPS board receiver (not the 'T' version). My 10 GHz LO is one of the older Microwave Associates brick type of oscillators. It has an internal 106.5 crystal oscillator that is in a crude oven. The 106.5 is multiplied by 96 to get the 10.224 GHz LO frequency. It would hold frequency fairly reasonably in my lab, but outside in the summer it would drift as much as 30 kHz. I installed a varactor diode on the quartz oscillator to control the frequency. I divided the 106.5 MHz down to 10 kHz and compared it with the 10 kHz out of the Jupiter in an exclusive OR gate. I used a one op amp filter circuit that had a time constant of 5 to 10 seconds - not critical, but just needs to be slow. If the GPS was 'warmed up' (it had been on in the last few hours), the 10 GHz LO will lock to within a few Hz of the 10.224 GHz in less than a minute after power on. I have some other frequency stability issues that I need to fix, but the GPS lock portion of the circuit works great. Look on eBay for GPS antennas. I use one of the small mag mount units. You can get one for around $6.00, shipping included. Also look on www.halted.com and search for GPS antenna. They have some (that I use) for $3.95, but charge $5.00 handling for under $20 - 1 is $8.95, 2 is $12.90, etc Let me know if I can help in any way. 73, Tom WB6UZZ --- On Sat, 1/28/12, Ray Xu rayxu...@gmail.com wrote: From: Ray Xu rayxu...@gmail.com Subject: [time-nuts] Building a GPSDO trouble using Jupiter-T To: time-nuts@febo.com Date: Saturday, January 28, 2012, 10:50 PM Hi guys I'm planning to build a GPSDO to use as a frequency ref for my GHz ventures. I've done research in what other people have built - but I have no experience working with long-term precision/stability products (nor do I have the equipment to do so -- I think). I'm using the Jupiter T (the one with the 10-pin header) GPS and its 10KHz output in an analog PLL that controls a 10MHz VCXO. It would be ideal for me that if I were to multiply the 10MHz output up to 10GHz, I would get about a few Hertz or so of inaccuracy. It would also be ideal if I can have a PLL lock time of a few minutes while maintaining accuracy. However, right now as I am trying to design my project, I can't find enough information on the web regarding the VCXO's (or the PLL oscillator, in this case) short term accuracy effect on output frequency. I know that its short term accuracy depends on the response time of the PLL, which also depends on the amount of jitter from the Jupiter-T's 10KHz output... I know that the longer the time constant for the PLL, the better accuracy, but I do not want to wait, literally, hours for it to lock... Also, what is the advantage of using a OCXO instead of a VCXO in terms of short-term accuracy? If the PLL time constant is only a few seconds, then a crystal shouldn't deviate in frequency by too much within a few seconds, assuming I'm using a crystal bought from a well-known manufacturer...or could it? I am inclined towards using oscillators that do not require any significant warm up time... For those who have experience using the Jupiter T GPS: I have bought this http://www.ebay.com/itm/Navman-jupiter-T-Tu60-GPS-Kit-1pps-10khz-GPS-Module-/260790984470but I could not get it to communicate via serial. So far, I do not have an antenna available and so the antenna port is just left disconnected. When I turn it on, there is a 1pps and 10KHz signal and the TX line is at logic high. However, I cannot get it to communicate to anything else, even a dumb terminal. It does not respond to when I send a message ID to it. (Because of computer difficulties, I am using the PicKit 2's UART tool). Is my device a dud or am I doing something wrong? Many inputs is highly appreciated. Thanks -- __ 73, Ray Xu KF5LJO ___ 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. -- __ 73, Ray Xu KF5LJO ___ time-nuts mailing list -- time
Re: [time-nuts] Building a GPSDO trouble using Jupiter-T
Hi Chris Thanks for your helpful input. What do you mean by average? Do you mean that the GPS and PLL must be kept on for 20 minutes to hours, or did you mean that the PLL loop filter must have a time constant of 20 minutes to several hours? To me, the latter seems really unpractical for analog filters...Yet I have seen many of them built using analog filters. Especially JAmes Miller's http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm and his FAQ says that the time to wait is perhaps 15 minutes or so to be usable. The previous GPSDO that James built has its schematic; the filter he used doesn't look like they're anywhere close to a time constant of 20 minutes. I may consider the Rb standard, but I'm more inclined on using GPS since I actually get to build some stuff on my own :-) Thanks again Ray Xu On Sun, Jan 29, 2012 at 6:52 PM, Chris Albertson albertson.ch...@gmail.comwrote: On Sat, Jan 28, 2012 at 10:50 PM, Ray Xu rayxu...@gmail.com wrote: Also, what is the advantage of using a OCXO instead of a VCXO in terms of short-term accuracy? If the PLL time constant is only a few seconds, then a crystal shouldn't deviate in frequency by too much within a few seconds, assuming I'm using a crystal bought from a well-known manufacturer...or could it? I am inclined towards using oscillators that do not require any significant warm up time... GPS is only a good reference if you average it over a long time period. (1000 to 10,000 seconds) There is more short term jitter in the GPS then in a decent crystal oscillator. So a very short time constant does you no good. Why use an OCXO? Because of the required long time constant. You need to average GPS for such a length of time (20 minutes to hours) that the ambient temperature will change during the averaging time. Of course you could take care that the temperature does not change but that is what an oven does.You can buy a pretty good OCXO for $20 or $25 How long? That depends on the required accuracy. You want 1Hz at 10GHz. That is 1E-10. Not super hard but no way will you have that 10 minutes after you apply power. If you need a portable standard look at those $40 rubidium nuts that are on eBay.It the 1E-10 level, after you calibrate it, if would stay on-frequency for days and not require much warm up. Chris Albertson Redondo Beach, California ___ 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. -- __ 73, Ray Xu KF5LJO ___ 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] Building a GPSDO trouble using Jupiter-T
Hi Erno Thanks for your suggestion; while it is convenient to have everything already planned out, I'm inclined on DIY'ing as much as I can :-) Ray Xu On Sun, Jan 29, 2012 at 1:01 AM, Erno Peres erniepe...@aol.com wrote: Hi Ray, please find on this link the info what you are looking for. http://www.jrmiller.demon.co.uk/projects/ministd/frqstd.htm Rgds Ernie. -Original Message- From: Ray Xu rayxu...@gmail.com To: time-nuts time-nuts@febo.com Sent: Sun, Jan 29, 2012 7:51 am Subject: [time-nuts] Building a GPSDO trouble using Jupiter-T Hi guys I'm planning to build a GPSDO to use as a frequency ref for my GHz ventures. I've done research in what other people have built - but I have no xperience working with long-term precision/stability products (nor do I ave the equipment to do so -- I think). I'm using the Jupiter T (the one with the 10-pin header) GPS and its 10KHz utput in an analog PLL that controls a 10MHz VCXO. It would be ideal for e that if I were to multiply the 10MHz output up to 10GHz, I would get bout a few Hertz or so of inaccuracy. It would also be ideal if I can ave a PLL lock time of a few minutes while maintaining accuracy. However, right now as I am trying to design my project, I can't find enough nformation on the web regarding the VCXO's (or the PLL oscillator, in this ase) short term accuracy effect on output frequency. I know that its hort term accuracy depends on the response time of the PLL, which also epends on the amount of jitter from the Jupiter-T's 10KHz output... I now that the longer the time constant for the PLL, the better accuracy, ut I do not want to wait, literally, hours for it to lock... Also, what is the advantage of using a OCXO instead of a VCXO in terms of hort-term accuracy? If the PLL time constant is only a few seconds, then crystal shouldn't deviate in frequency by too much within a few seconds, ssuming I'm using a crystal bought from a well-known manufacturer...or ould it? I am inclined towards using oscillators that do not require any ignificant warm up time... For those who have experience using the Jupiter T GPS: have bought this ttp:// www.ebay.com/itm/Navman-jupiter-T-Tu60-GPS-Kit-1pps-10khz-GPS-Module-/260790984470but could not get it to communicate via serial. So far, I do not have n ntenna available and so the antenna port is just left disconnected. When turn it on, there is a 1pps and 10KHz signal and the TX line is at logic igh. However, I cannot get it to communicate to anything else, even a umb terminal. It does not respond to when I send a message ID to it. Because of computer difficulties, I am using the PicKit 2's UART tool). s my device a dud or am I doing something wrong? Many inputs is highly appreciated. Thanks -- _ 3, Ray Xu F5LJO __ ime-nuts mailing list -- time-nuts@febo.com o unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts nd 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. -- __ 73, Ray Xu KF5LJO ___ 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] Building a GPSDO trouble using Jupiter-T
Hi guys I'm planning to build a GPSDO to use as a frequency ref for my GHz ventures. I've done research in what other people have built - but I have no experience working with long-term precision/stability products (nor do I have the equipment to do so -- I think). I'm using the Jupiter T (the one with the 10-pin header) GPS and its 10KHz output in an analog PLL that controls a 10MHz VCXO. It would be ideal for me that if I were to multiply the 10MHz output up to 10GHz, I would get about a few Hertz or so of inaccuracy. It would also be ideal if I can have a PLL lock time of a few minutes while maintaining accuracy. However, right now as I am trying to design my project, I can't find enough information on the web regarding the VCXO's (or the PLL oscillator, in this case) short term accuracy effect on output frequency. I know that its short term accuracy depends on the response time of the PLL, which also depends on the amount of jitter from the Jupiter-T's 10KHz output... I know that the longer the time constant for the PLL, the better accuracy, but I do not want to wait, literally, hours for it to lock... Also, what is the advantage of using a OCXO instead of a VCXO in terms of short-term accuracy? If the PLL time constant is only a few seconds, then a crystal shouldn't deviate in frequency by too much within a few seconds, assuming I'm using a crystal bought from a well-known manufacturer...or could it? I am inclined towards using oscillators that do not require any significant warm up time... For those who have experience using the Jupiter T GPS: I have bought this http://www.ebay.com/itm/Navman-jupiter-T-Tu60-GPS-Kit-1pps-10khz-GPS-Module-/260790984470but I could not get it to communicate via serial. So far, I do not have an antenna available and so the antenna port is just left disconnected. When I turn it on, there is a 1pps and 10KHz signal and the TX line is at logic high. However, I cannot get it to communicate to anything else, even a dumb terminal. It does not respond to when I send a message ID to it. (Because of computer difficulties, I am using the PicKit 2's UART tool). Is my device a dud or am I doing something wrong? Many inputs is highly appreciated. Thanks -- __ 73, Ray Xu KF5LJO ___ 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.
