Re: [time-nuts] nubie querie
Concerning my query about what's good enough to count as a contact... We've done Moonbounce with 3mW (Hobart - Dwingeloo) in JT65 - but a 26m and a 25m dish is stretching 'amateur' a bit again. Googling for JT65 finds a nice paper: http://www.arrl.org/FandES/field/regulations/techchar/18JT65.pdf The JT65 Communications Protocol Joe Taylor, K1JT It's a fun read. 17 pages. The basic idea seems to be that amateurs (hams) have to exchange station IDs. That's more than a few bits, but not a huge number. JT65 is a compact protocol for doing that in a (very) weak signal environment. Their packet format is 72 bits expanded to 378 by forward error correcting. On top of that, they use half of the time for a synchronizing signal so the receiver can find the transmitter's time and frequency. Each 72 bit packet takes 1 minute to send. Their modulation scheme is 1 of 65 tones. 6 bits per baud. The extra tone is the synchronizing signal. -- 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] nubie querie (Earth Venus Earth, done!)
Sorry, it's already been done I believe. http://freenet-homepage.de/dl4yhf/speclab/earth_venus_earth.htm Some years ago, like nearly 20, I helped some friends and built a 224 element broadside colinear aray for EME. It (eventualy) worked realy well. Echoes could be heard under good conditions with 5W I seem to recall (and no computer driven DSP tools then.) We also did so far (as we know) the only mobile EME contact, between G8MBI/m and W5UN. As a result, I think my Land Rover holds the world 2m mobile DX record (regardless how you calculate it.) Also the World EME land speed record (45MPH). http://www.rfham.com/g8mbi/mbi.htm and scroll down about 3/4 down the page. 73. Dave G0WBX. Not sure about being a fully qualified Time Nut, but a Nut none the less! The sticker on the back door of the Landie these days also confims it. This vehicle may contain nuts -Original Message- Date: Wed, 10 Mar 2010 14:32:33 -0700 From: David Forbes dfor...@dakotacom.net Subject: Re: [time-nuts] nubie querie To: Discussion of precise time and frequency measurement time-nuts@febo.com Message-ID: 4b980ff1.7040...@dakotacom.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed Hal Murray wrote: This, and similar impressive accomplishments, has prompted some lunchtime discussion at work (JPL).. One of us (N5BF) has been contemplating what it would take to do an amateur EarthVenusEarth (after some of his experiments doing EME with 5 watts).. Perhaps a better question is: What is the bandwidth? What sort of signal do I have to receive in order to claim contact? Is one bit/blob of energy at the right time/frequency good enough, or do I have to demodulate the signal and extract a few bits of data? Marconi claimed credit for the first transatlantic communication by sending the letter S in Morse code. That sounds like a fine standard - one byte of data. It's statistically significant. With regard to the restoration and use of a derelict radio telescope for amateur radio, that's a fine example of amateurs putting themselves to a big task and succeeding. I work on radio telescopes, so I know how big a task that is. --David Forbes -- ___ 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] nubie querie
Hal Murray wrote: Concerning my query about what's good enough to count as a contact... We've done Moonbounce with 3mW (Hobart - Dwingeloo) in JT65 - but a 26m and a 25m dish is stretching 'amateur' a bit again. Googling for JT65 finds a nice paper: http://www.arrl.org/FandES/field/regulations/techchar/18JT65.pdf The JT65 Communications Protocol Joe Taylor, K1JT It's a fun read. 17 pages. The basic idea seems to be that amateurs (hams) have to exchange station IDs. That's more than a few bits, but not a huge number. JT65 is a compact protocol for doing that in a (very) weak signal environment. Their packet format is 72 bits expanded to 378 by forward error correcting. On top of that, they use half of the time for a synchronizing signal so the receiver can find the transmitter's time and frequency. Each 72 bit packet takes 1 minute to send. Their modulation scheme is 1 of 65 tones. 6 bits per baud. The extra tone is the synchronizing signal. 6 bits per symbol. 1 baud is 1 symbol per second. Happy to see someone using baud, just unhappy about seeing it being used incorrectly. An amusing error was found in one of our early datasheets. For some reason they wanted to tell the signal rate, so they said 1,0625 GBaud/s. I found that very amusing to have symbol acceleration... it gets faster every second!!! Just keep a fixed bit/symbol ratio and you have a hell of a product. Later in life it will transport all of universe into a black hole. 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] nubie querie
mag...@rubidium.dyndns.org said: Their modulation scheme is 1 of 65 tones. 6 bits per baud. The extra tone is the synchronizing signal. 6 bits per symbol. 1 baud is 1 symbol per second. Happy to see someone using baud, just unhappy about seeing it being used incorrectly. Thanks for correcting my screwup. -- 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] nubie querie
Hal Murray wrote: mag...@rubidium.dyndns.org said: Their modulation scheme is 1 of 65 tones. 6 bits per baud. The extra tone is the synchronizing signal. 6 bits per symbol. 1 baud is 1 symbol per second. Happy to see someone using baud, just unhappy about seeing it being used incorrectly. Thanks for correcting my screwup. No worries, I am sure you will return the favour when I screw up. I still wonder when people will limit themselves to using bandwidth only for denoting a frequency range. 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] nubie querie (Earth Venus Earth, done!)
I think the Dutch have done EVE; seems something passed by on Moon-Net in the past year... Don Dave Baxter Sorry, it's already been done I believe. http://freenet-homepage.de/dl4yhf/speclab/earth_venus_earth.htm Some years ago, like nearly 20, I helped some friends and built a 224 element broadside colinear aray for EME. It (eventualy) worked realy well. Echoes could be heard under good conditions with 5W I seem to recall (and no computer driven DSP tools then.) We also did so far (as we know) the only mobile EME contact, between G8MBI/m and W5UN. As a result, I think my Land Rover holds the world 2m mobile DX record (regardless how you calculate it.) Also the World EME land speed record (45MPH). http://www.rfham.com/g8mbi/mbi.htm and scroll down about 3/4 down the page. 73. Dave G0WBX. Not sure about being a fully qualified Time Nut, but a Nut none the less! The sticker on the back door of the Landie these days also confims it. This vehicle may contain nuts -Original Message- Date: Wed, 10 Mar 2010 14:32:33 -0700 From: David Forbes dfor...@dakotacom.net Subject: Re: [time-nuts] nubie querie To: Discussion of precise time and frequency measurement time-nuts@febo.com Message-ID: 4b980ff1.7040...@dakotacom.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed Hal Murray wrote: This, and similar impressive accomplishments, has prompted some lunchtime discussion at work (JPL).. One of us (N5BF) has been contemplating what it would take to do an amateur EarthVenusEarth (after some of his experiments doing EME with 5 watts).. Perhaps a better question is: What is the bandwidth? What sort of signal do I have to receive in order to claim contact? Is one bit/blob of energy at the right time/frequency good enough, or do I have to demodulate the signal and extract a few bits of data? Marconi claimed credit for the first transatlantic communication by sending the letter S in Morse code. That sounds like a fine standard - one byte of data. It's statistically significant. With regard to the restoration and use of a derelict radio telescope for amateur radio, that's a fine example of amateurs putting themselves to a big task and succeeding. I work on radio telescopes, so I know how big a task that is. --David Forbes -- ___ 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. -- Dr. Don Latham AJ7LL Six Mile Systems LLP 17850 Six Mile Road POB 134 Huson, MT, 59846 VOX 406-626-4304 www.lightningforensics.com www.sixmilesystems.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] nubie querie (Earth Venus Earth, done!)
At 20.33 11/03/2010, you wrote: I think the Dutch have done EVE; seems something passed by on Moon-Net in the past year... Don AMSAT DL, one year ago, using 6kW CW (injection locked magnetron) on 13 cm and a big parabolic reflector. See http://www.arrl.org/news/stories/2009/03/31/10738/?nc=1 73 - Marco IK1ODO ___ 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] nubie querie
Hi Jim, jimlux wrote: This, and similar impressive accomplishments, has prompted some lunchtime discussion at work (JPL).. One of us (N5BF) has been contemplating what it would take to do an amateur EarthVenusEarth (after some of his experiments doing EME with 5 watts).. Has recently been done by German amateurs in Bochum: http://www.southgatearc.org/news/march2009/eve.htm We've done Moonbounce with 3mW (Hobart - Dwingeloo) in JT65 - but a 26m and a 25m dish is stretching 'amateur' a bit again. So, when talking about amateur accomplishments.. where do you draw the line on using big stuff. If you're an amateur who happens to have access to Arecibo or to a DSN 70m dish, is that *really* an amateur contact/event? For Camras, I do now have to point out that the dish had been unused for 13 years, and apart from the construction itself, nothing was really in a serviceable state anymore. This means that we installed new engines and the hardware/software to drive them, gearbox modifications, new antennas, preamps, receivers, backends, pulsar-processing, computing, networking and much more. It's not as if we were handed the key to a working telescope - in fact, the first work was mucking out the dirt and dead animals that had gathered inside... So, when talking about amateur accomplishments.. where do you draw the line on using big stuff. Singlehandedly is a poor discriminator, as doing things like this in a group is great fun, Fabrication seems more relevant - but in the end, what's really the point of drawing such an arbitrary line, as long as we're having a great time and accomplish things? The great equalizer here is simply the ongoing rapid technological progress. Hobby-prized access to fun toys like Rubidiums (does anyone have an H-maser to spare though? ;-), FPGAs and fast A/D converters make things possible for amateurs nowadays that were out of reach for professionals just a decade ago. Working on a dish that is more than 50 years old really puts this in perspective, and we as amateurs have already improved its performance in some aspects beyond what it could do in its 'professional' life (thanks of course to this 13 year gap). Regards, Paul Boven. ___ 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] nubie querie
This, and similar impressive accomplishments, has prompted some lunchtime discussion at work (JPL).. One of us (N5BF) has been contemplating what it would take to do an amateur EarthVenusEarth (after some of his experiments doing EME with 5 watts).. Perhaps a better question is: What is the bandwidth? What sort of signal do I have to receive in order to claim contact? Is one bit/blob of energy at the right time/frequency good enough, or do I have to demodulate the signal and extract a few bits of data? So, when talking about amateur accomplishments.. where do you draw the line on using big stuff. If you're an amateur who happens to have access to Arecibo or to a DSN 70m dish, is that *really* an amateur contact/event? I think the traditional test for an amateur is do you get paid for it. (Yes, it helps to be independently wealthy.) Even if you build your own antenna, there is the question of where do you start. Is it OK to buy a dish if I build the mount? Can I buy steel pipe or do I have to start from iron ore? I suspect if you look at other amateur activities (say sports), there are examples equivalent to scrounging time on Arecibo. My 2 cents... You get credit for the part that you do. Anything goes as long as you are honest about what you do. If you buy the electronics and build the antenna, you get credit for building the antenna. If you build the electronics and buy (or scrounge) the antenna, then you get credit for the electronics. ... Some people are really good at scrounging. -- 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] nubie querie
Hal Murray wrote: This, and similar impressive accomplishments, has prompted some lunchtime discussion at work (JPL).. One of us (N5BF) has been contemplating what it would take to do an amateur EarthVenusEarth (after some of his experiments doing EME with 5 watts).. Perhaps a better question is: What is the bandwidth? What sort of signal do I have to receive in order to claim contact? Is one bit/blob of energy at the right time/frequency good enough, or do I have to demodulate the signal and extract a few bits of data? Marconi claimed credit for the first transatlantic communication by sending the letter S in Morse code. That sounds like a fine standard - one byte of data. It's statistically significant. With regard to the restoration and use of a derelict radio telescope for amateur radio, that's a fine example of amateurs putting themselves to a big task and succeeding. I work on radio telescopes, so I know how big a task that is. --David Forbes ___ 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] nubie querie
On 3/10/10, David Forbes dfor...@dakotacom.net wrote: With regard to the restoration and use of a derelict radio telescope for amateur radio, that's a fine example of amateurs putting themselves to a big task and succeeding. I work on radio telescopes, so I know how big a task that is. Here in Italy, radio telescopes, brand new ones like the Sardinia Radio Telescope, get abandoned just a minute after they've been built (or a minute before maybe). I whish radio amateurs could have any role in rescuing such a great tool for research and science (64m dish). Government looks not so interested in science here. Frank IZ8DWF (IS0FKQ some years ago) ___ 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] nubie querie
This thread mentioned puilsars and the best clocks. Here are some comments from those really in the know: == Latest Al+ clock comparision at NIST is at better than 10^-17 level see. http://arxiv.org/abs/0911.4527 == rich...@karlquist.com said: I vaguely remember reading that pulsars have some fantastic stability like 1E-20. [snip] Pulsars decelerate due to electrodynamic drag -- the reaction torque from the pulsar's external magnetic field trying to spin the plasma surrounding the pulsar, and generating MHD waves in this plasma. Because the plasma density varies randomly, the drag torque varies randomly. Some pulsars are subject to other torques, for example because they have close binary companions. Even in the absence of external torque, some pulsars change angular velocity abruptly because their moments of inertia change when starquakes (like earthquakes, but in the neutron crystalline solid body of the star) occur. In early 1969, shortly after the Crab Nebula pulsar (the first so- called millisecond pulsar, with a rotation rate of of about 30 revs per second) had been discovered, and (IIRC) before a starquake had been observed, we began observing this pulsar at Arecibo Observatory in Puerto Rico. In one daily observation that involved about an hour of averaging, we could determine the pulsar's rotation phase angle with precision of about 50 microradians. (This was after removing the time-varying propagation group-delay due to plasma between us and the pulsar. To distinguish the plasma delay, we observed the pulsar concurrently at radio frequencies ranging from 40 MHz to 430 or 611 MHz.) Within a few months, we found that the pulsar was a rotten clock relative to the Observatory's H-P Cesium-beam- referenced clock, which we checked daily against the Loran-C ground- wave (over sea water, actually) signal from Jupiter, FL. Since then, other pulsars have turned out to be more stable (and others less so). AFAIK, none has yet beaten a good atomic clock. Pulsar PSR1937+21, discovered in 1982, attracted attention because its rotation rate was about 600 revs per second. (So it was more deserving of the title, millisecond pulsar.) In its first two years of being observed, it did not have a glitch or starquake. In two years, about 2 x 10^11 rotations were observed, and the rotation phase had been determined within about about 1/160th of a revolution, so the average spin rate was known within about a part in 10^13. However, in the next twenty-five years, its spin rate on a time-scale of about one year turned out to be no more stable than about 1 in 10^13. AFAIK. It's been a few years since I read anything about this pulsar. Millisecond pulsars are more stable than slower pulsars, and hope has been expressed that, when thousands or tens of thousands of these pulsars have been discovered and can be observed nearly continuously, the ensemble of this many pulsars will allow establishment of a pulsar- based standard of time having stability, on a time-scale of about one year, of a few parts in 10^15. AFAIK, such a standard remains a dream, not a reality. ___ 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] nubie querie
Hal Murray wrote: This, and similar impressive accomplishments, has prompted some lunchtime discussion at work (JPL).. One of us (N5BF) has been contemplating what it would take to do an amateur EarthVenusEarth (after some of his experiments doing EME with 5 watts).. Perhaps a better question is: What is the bandwidth? What sort of signal do I have to receive in order to claim contact? Is one bit/blob of energy at the right time/frequency good enough, or do I have to demodulate the signal and extract a few bits of data? So, when talking about amateur accomplishments.. where do you draw the line on using big stuff. If you're an amateur who happens to have access to Arecibo or to a DSN 70m dish, is that *really* an amateur contact/event? I think the traditional test for an amateur is do you get paid for it. (Yes, it helps to be independently wealthy.) Well, that's sort of the 18th/19th century model, certainly. Lavoisier wasn't paid to figure chemistry out. Neither did John Strutt, 3rd Baron Rayleigh. But is that an appropriate model for today? Even if you build your own antenna, there is the question of where do you start. Is it OK to buy a dish if I build the mount? Can I buy steel pipe or do I have to start from iron ore? I've always wanted to start with smelting, but my wife says no cupola furnace in the backyard (this after I was pointing out the books on this in the Lindsay Books catalog). I suspect if you look at other amateur activities (say sports), there are examples equivalent to scrounging time on Arecibo. Sure.. and the sponging off others has historical precedent, for DXpeditions and 8000 meter peak attempts alike. My 2 cents... You get credit for the part that you do. Anything goes as long as you are honest about what you do. If you buy the electronics and build the antenna, you get credit for building the antenna. If you build the electronics and buy (or scrounge) the antenna, then you get credit for the electronics. ... Some people are really good at scrounging. ___ 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] nubie querie
If you like starting from scratch, get a copy of Procedures in Experimental Physics by John Strong. -John === Hal Murray wrote: This, and similar impressive accomplishments, has prompted some lunchtime discussion at work (JPL).. One of us (N5BF) has been contemplating what it would take to do an amateur EarthVenusEarth (after some of his experiments doing EME with 5 watts).. Perhaps a better question is: What is the bandwidth? What sort of signal do I have to receive in order to claim contact? Is one bit/blob of energy at the right time/frequency good enough, or do I have to demodulate the signal and extract a few bits of data? So, when talking about amateur accomplishments.. where do you draw the line on using big stuff. If you're an amateur who happens to have access to Arecibo or to a DSN 70m dish, is that *really* an amateur contact/event? I think the traditional test for an amateur is do you get paid for it. (Yes, it helps to be independently wealthy.) Well, that's sort of the 18th/19th century model, certainly. Lavoisier wasn't paid to figure chemistry out. Neither did John Strutt, 3rd Baron Rayleigh. But is that an appropriate model for today? Even if you build your own antenna, there is the question of where do you start. Is it OK to buy a dish if I build the mount? Can I buy steel pipe or do I have to start from iron ore? I've always wanted to start with smelting, but my wife says no cupola furnace in the backyard (this after I was pointing out the books on this in the Lindsay Books catalog). I suspect if you look at other amateur activities (say sports), there are examples equivalent to scrounging time on Arecibo. Sure.. and the sponging off others has historical precedent, for DXpeditions and 8000 meter peak attempts alike. My 2 cents... You get credit for the part that you do. Anything goes as long as you are honest about what you do. If you buy the electronics and build the antenna, you get credit for building the antenna. If you build the electronics and buy (or scrounge) the antenna, then you get credit for the electronics. ... Some people are really good at scrounging. ___ 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] nubie querie
J. Forster wrote: If you like starting from scratch, get a copy of Procedures in Experimental Physics by John Strong. -John And, relevant to the thermal time constant discussion.. That book has a great section on thermal diffusion and conductivity, along with a chart of material properties. A newer book is building scientific apparatus by Moore, et al. There's a whole section on precision temperature control (where precision means milliKelvin).. But not as much fundamentals stuff as in Strong. e.g. Moore assumes you can buy a vacuum pump, Strong tells you how to build one..what a difference 60 years makes. But even Strong doesn't tell you how to make cast iron from ore. Lindsay Books is your friend, then. ___ 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] nubie querie
jimlux wrote: J. Forster wrote: If you like starting from scratch, get a copy of Procedures in Experimental Physics by John Strong. -John And, relevant to the thermal time constant discussion.. That book has a great section on thermal diffusion and conductivity, along with a chart of material properties. A newer book is building scientific apparatus by Moore, et al. There's a whole section on precision temperature control (where precision means milliKelvin).. Yes, it was coauthored by my thesis adviser, CC Davis. I was working for him while he was writing his sections. Never noticed anything of mine in it, though. -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] nubie querie
Paul Boven wrote: Hi Tom, everyone, Tom Van Baak wrote: See: http://www.leapsecond.com/museum/pulsar for some pulsar ADEV stability plots and links to many research papers with all the details. Your page starts with the question if it was possible for an amateur to receive pulsar signals?. Turns out you can, at least the particular bunch of amateurs who have been restoring the 25m Dwingeloo radio telescope (http://www.camras.nl). This, and similar impressive accomplishments, has prompted some lunchtime discussion at work (JPL).. One of us (N5BF) has been contemplating what it would take to do an amateur EarthVenusEarth (after some of his experiments doing EME with 5 watts).. So, when talking about amateur accomplishments.. where do you draw the line on using big stuff. If you're an amateur who happens to have access to Arecibo or to a DSN 70m dish, is that *really* an amateur contact/event? The same thing applies to timenuttery, to a certain extent. So we thought.. if it's something that a single amateur can feasibly do single handedly. Surely, no amateur is going to build Arecibo or a 70m dish in their backyard.. but wait, what if you're Paul Allen building the ATA at Hat Creek. Should happening to be wealthy enough to buy all the toys exclude you.. after all, it's the amateur aspect, not the poverty aspect. Or, maybe it's the fabrication of the equipment that's the relevant thing. I know I'd be more impressed by someone building a Cesium clock from scratch in their garage more than just buying one off the shelf, even if buying one is cheaper. Kind of like making your own vacuum tubes. And, even, since those of us sitting around the lunch table do RF work of one sort or another for a living, is *anything* we do with RF truly amateur (leaving aside legalisms like pecuniary interests, etc.). Maybe it's a sort of fuzzy definition.. you can fit it in a suburban backyard (leaving out the 70m dishes, but not the EME array, as long as you're not in the W5UN category) Or time nuts wise, some aspect of self fabrication, whether it be hardware, software, or even just an unusual configuration or kind of clock. Could you do this with a more modest antenna? The lesser gain would need to be compensated for by using as much bandwidth as possible (which needs de-dispersion), and folding the signal by the pulsar period. Folding in turn requires a stable clock, and compensating for the doppler shift caused by the Earth's motions. I would say that receiving the brightest pulsars is within reach of the bigger EME stations - but still working on the calculations (and demonstration) to back this up. This is kind of fascinating... When I got started in home time nut territory, it was because I got a Z3801.. as a coworker put it, how often do you have something accurate to way better than a part per billion in your garage. ___ 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] nubie querie
tvb... Not to kick sand in your face, but it seems that in order for your automated turn-over device to work, as well as to accurately measure the time intervals, you would need a means to determine when the sand quits flowing. Possibly an accelerometer or microphone, with the added benefit of being able to hear the close-in phase noise. I admire your dedication to monitoring the hour long periods of the sand timer so diligently. Truly a time-nut! Regards, Tom Holmes, N8ZM Tipp City, OH EM79xx -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van Baak Sent: Friday, March 05, 2010 1:44 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] nubie querie In the last slide you show a sand timer. Do you have accuracy data for it? Hi Brooke, The past 3 hours the one hour timer measures 56:24, 56:19, and 56:30. That's at 67 F room temp. Somewhere I have enough clean data to compute the ADEV; it's more stable than accurate. It also has a tempco (one day when my wife wasn't looking I collected data inside the kitchen refrigerator, and oven). I would guess it has very little dependence on barometric pressure or humidity since all the sand is sealed inside the blown glass bulb. Eventually I will mechanically automate the hourly turn-over and get 24x7 long-term data. If I also model the tempco it may be possible to temperature compensate the rate error. I don't know where the flicker floor will be. My prediction is this hour-glass will gradually speed up as the glass or the sand slowly wear over time. /tvb ___ 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] nubie querie
Hi Even defining when the sand timer is done is not a real simple thing. Waiting for that very last particle to drop may not be the best approach. Bob On Mar 5, 2010, at 9:20 AM, Tom Holmes, N8ZM wrote: tvb... Not to kick sand in your face, but it seems that in order for your automated turn-over device to work, as well as to accurately measure the time intervals, you would need a means to determine when the sand quits flowing. Possibly an accelerometer or microphone, with the added benefit of being able to hear the close-in phase noise. I admire your dedication to monitoring the hour long periods of the sand timer so diligently. Truly a time-nut! Regards, Tom Holmes, N8ZM Tipp City, OH EM79xx -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van Baak Sent: Friday, March 05, 2010 1:44 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] nubie querie In the last slide you show a sand timer. Do you have accuracy data for it? Hi Brooke, The past 3 hours the one hour timer measures 56:24, 56:19, and 56:30. That's at 67 F room temp. Somewhere I have enough clean data to compute the ADEV; it's more stable than accurate. It also has a tempco (one day when my wife wasn't looking I collected data inside the kitchen refrigerator, and oven). I would guess it has very little dependence on barometric pressure or humidity since all the sand is sealed inside the blown glass bulb. Eventually I will mechanically automate the hourly turn-over and get 24x7 long-term data. If I also model the tempco it may be possible to temperature compensate the rate error. I don't know where the flicker floor will be. My prediction is this hour-glass will gradually speed up as the glass or the sand slowly wear over time. /tvb ___ 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] nubie querie
Don Collie jnr wrote: I`m not sure that questions like these is welcome on this list, but here goes anyway : 1/ What are the the 10 sources of the most constant [invariant] frequencies known to man, in order of decreacing constancy? Four immediately come to mind. I vaguely remember reading that pulsars have some fantastic stability like 1E-20. I don't remember how they established this. 2/ What is the mechanism in an oscillator, that is responsible for phase noise? [In only one sentence please] Thermal (Johnson) noise in the resonator and thermal and shot noise in the active device. If this is known, then it becomes easier to design low phase noise oscillators. Perhaps, but just knowing the mechanism doesn't tell you that the phase noise is inversely proportional to loaded Q, which you would also need to know to optimize phase noise. I hope you enjoy these questions,.Don. ___ 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] nubie querie
Hi Then there's the phase noise of the pulsar oscillator - For a simple crystal oscillator the two word answer might be Leeson's model. That of course is a cop out since it clearly defines multiple things that contribute to phase noise. Bob On Mar 5, 2010, at 9:39 AM, Richard (Rick) Karlquist wrote: Don Collie jnr wrote: I`m not sure that questions like these is welcome on this list, but here goes anyway : 1/ What are the the 10 sources of the most constant [invariant] frequencies known to man, in order of decreacing constancy? Four immediately come to mind. I vaguely remember reading that pulsars have some fantastic stability like 1E-20. I don't remember how they established this. 2/ What is the mechanism in an oscillator, that is responsible for phase noise? [In only one sentence please] Thermal (Johnson) noise in the resonator and thermal and shot noise in the active device. If this is known, then it becomes easier to design low phase noise oscillators. Perhaps, but just knowing the mechanism doesn't tell you that the phase noise is inversely proportional to loaded Q, which you would also need to know to optimize phase noise. I hope you enjoy these questions,.Don. ___ 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] nubie querie
If the time duration of the sand timer is defined as when the first grain of sand lands on the bottom, until the last grain of sand lands on the pile of sand on the bottom, maybe an optical circuit may sense the passing and interruption with a light beam. Possibly the optical sensor mounted in the restricted center could sense the first grain starting to pass and when the last grain has passed. That my change the definition, but it should be repeatable. The acoustic approach has merit. I could then apply some DSP and more test equipment. Much easier than listening to the grass grow. I personally like definitive starts and stops, to stay within my attention span. Stan, W1LE Bob Camp wrote: Hi Even defining when the sand timer is done is not a real simple thing. Waiting for that very last particle to drop may not be the best approach. Bob On Mar 5, 2010, at 9:20 AM, Tom Holmes, N8ZM wrote: tvb... Not to kick sand in your face, but it seems that in order for your automated turn-over device to work, as well as to accurately measure the time intervals, you would need a means to determine when the sand quits flowing. Possibly an accelerometer or microphone, with the added benefit of being able to hear the close-in phase noise. I admire your dedication to monitoring the hour long periods of the sand timer so diligently. Truly a time-nut! Regards, Tom Holmes, N8ZM Tipp City, OH EM79xx -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van Baak Sent: Friday, March 05, 2010 1:44 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] nubie querie In the last slide you show a sand timer. Do you have accuracy data for it? Hi Brooke, The past 3 hours the one hour timer measures 56:24, 56:19, and 56:30. That's at 67 F room temp. Somewhere I have enough clean data to compute the ADEV; it's more stable than accurate. It also has a tempco (one day when my wife wasn't looking I collected data inside the kitchen refrigerator, and oven). I would guess it has very little dependence on barometric pressure or humidity since all the sand is sealed inside the blown glass bulb. Eventually I will mechanically automate the hourly turn-over and get 24x7 long-term data. If I also model the tempco it may be possible to temperature compensate the rate error. I don't know where the flicker floor will be. My prediction is this hour-glass will gradually speed up as the glass or the sand slowly wear over time. /tvb ___ 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] nubie querie
The variability will depend on friction between particles and the last particle's physical slide down the glass! At 05-03-10, you wrote: Hi Even defining when the sand timer is done is not a real simple thing. Waiting for that very last particle to drop may not be the best approach. Bob On Mar 5, 2010, at 9:20 AM, Tom Holmes, N8ZM wrote: tvb... Not to kick sand in your face, but it seems that in order for your automated turn-over device to work, as well as to accurately measure the time intervals, you would need a means to determine when the sand quits flowing. Possibly an accelerometer or microphone, with the added benefit of being able to hear the close-in phase noise. I admire your dedication to monitoring the hour long periods of the sand timer so diligently. Truly a time-nut! Regards, Tom Holmes, N8ZM Tipp City, OH EM79xx ___ 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] nubie querie
Hi So can you / do you actually *see* the last grain in the hourglass in question? If we are looking at something that is not observed in normal operation we have re-defined the function of the device. Bob On Mar 5, 2010, at 10:50 AM, Raj wrote: The variability will depend on friction between particles and the last particle's physical slide down the glass! At 05-03-10, you wrote: Hi Even defining when the sand timer is done is not a real simple thing. Waiting for that very last particle to drop may not be the best approach. Bob On Mar 5, 2010, at 9:20 AM, Tom Holmes, N8ZM wrote: tvb... Not to kick sand in your face, but it seems that in order for your automated turn-over device to work, as well as to accurately measure the time intervals, you would need a means to determine when the sand quits flowing. Possibly an accelerometer or microphone, with the added benefit of being able to hear the close-in phase noise. I admire your dedication to monitoring the hour long periods of the sand timer so diligently. Truly a time-nut! Regards, Tom Holmes, N8ZM Tipp City, OH EM79xx ___ 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] nubie querie
All of this reminds me of a cartoon I saw ages ago, I think was called BC. Characters were from the cave-man era. Regardless, in one cartoon there is a guy sitting in the middle of a desert. His friend comes up and asks him what he is doing. The guy replies that he is going to count all of the sand in the desert. His friend says - you are crazy, that will take forever. The guys says, what you think, I am that stupid? I just count every other one, when I am done I will just double it. Regards - Mike Mike B. Feher, N4FS 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Bob Camp Sent: Friday, March 05, 2010 11:02 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] nubie querie Hi So can you / do you actually *see* the last grain in the hourglass in question? If we are looking at something that is not observed in normal operation we have re-defined the function of the device. Bob On Mar 5, 2010, at 10:50 AM, Raj wrote: The variability will depend on friction between particles and the last particle's physical slide down the glass! At 05-03-10, you wrote: Hi Even defining when the sand timer is done is not a real simple thing. Waiting for that very last particle to drop may not be the best approach. Bob On Mar 5, 2010, at 9:20 AM, Tom Holmes, N8ZM wrote: tvb... Not to kick sand in your face, but it seems that in order for your automated turn-over device to work, as well as to accurately measure the time intervals, you would need a means to determine when the sand quits flowing. Possibly an accelerometer or microphone, with the added benefit of being able to hear the close-in phase noise. I admire your dedication to monitoring the hour long periods of the sand timer so diligently. Truly a time-nut! Regards, Tom Holmes, N8ZM Tipp City, OH EM79xx ___ 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] nubie querie
At 10:25 AM -0800 3/4/10, Brooke Clarke wrote: Hi Tom: In the last slide you show a sand timer. Do you have accuracy data for it? Wouldn't that depend on the consistency with which the human flips the hour glass? They don't flip themselves, you know. -- --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] nubie querie
You've not seen me on a bad day - I've been known to flip quite often! :-) Dave -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of David Forbes Sent: 05 March 2010 16:20 To: Discussion of precise time and frequency measurement; Tom Van Baak Subject: Re: [time-nuts] nubie querie At 10:25 AM -0800 3/4/10, Brooke Clarke wrote: Hi Tom: In the last slide you show a sand timer. Do you have accuracy data for it? Wouldn't that depend on the consistency with which the human flips the hour glass? They don't flip themselves, you know. -- --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. ___ 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] nubie querie
Like it very well On Fri, Mar 5, 2010 at 11:12 AM, Mark Sims hol...@hotmail.com wrote: Google USB Hourglass or visit http://home.comcast.net/~hourglass/ and you will see that it has already been done. His application was as a random number generator. Should be available as a kit soon... _ Hotmail: Free, trusted and rich email service. http://clk.atdmt.com/GBL/go/201469228/direct/01/ ___ 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] nubie querie
rich...@karlquist.com said: I vaguely remember reading that pulsars have some fantastic stability like 1E-20. I don't remember how they established this. Do you remember how long ago you read that? It might have been some handwaving back before they had good data. For a while, the astronomers were seriously trying to take back the official clock from the physicists. They didn't make it. I think a lot of the interest started when somebody discovered a pulsar ticking at close to 1 KHz. That was in 1982. They have collected enough data to see things like star-quakes which are glitches in the rotation rate due to geologic type shifts similar to the recent discussion of 1.26 microseconds per day from the Chile quake. They decay by gravitational radiation and speed up when accretion adds more momentum and energy. Scientists predict pulsar starquakes June 5, 2006 http://www.lanl.gov/news/index.php/fuseaction/home.story/story_id/8528 Middleditch and his team have discovered that for one particular pulsar, named PSR J0537-6910, the time until the next quake is proportional to the size of the last quake. Using this simple formula, the scientists have been able to aim NASA's Rossi X-ray Timing Explorer at the pulsar a few days before a quake to watch the event unfold. [A fun read.] -- 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] nubie querie
I vaguely remember reading that pulsars have some fantastic stability like 1E-20. I don't remember how they established this. Rick, See: http://www.leapsecond.com/museum/pulsar for some pulsar ADEV stability plots and links to many research papers with all the details. /tvb ___ 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] nubie querie
Even defining when the sand timer is done is not a real simple thing. Waiting for that very last particle to drop may not be the best approach. Bob Correct. Marking time with an hour glass is not that different from marking time with a 1PPS. Each signal has a rise time; one picks the appropriate live trigger level or sampled slope waveform model to minimize jitter. Waiting for the last grain is like waiting for the last millivolt of a TTL 1PPS pulse; no one does that. Note that [this] hourglass interval has a standard deviation on the order of 10 seconds. So my initial goal is 1 second timing resolution, which turns out to be pretty easy to do optically. Whether sand or cesium, phase comparators have a minimum resolution. While lower resolution is better, if the ADEV of the DUT is too far above the ADEV of the comparator then that resolution is wasted. So detection to a granularity of 1 second is sufficient for this application. /tvb ___ 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] nubie querie
OK then if you ground up cesium azide and put it in the hour glass wouldn't you have a cesium clock at much lower cost (And accuracy) then an HP?? Might last quite a while also. On Fri, Mar 5, 2010 at 1:53 PM, Tom Van Baak t...@leapsecond.com wrote: Even defining when the sand timer is done is not a real simple thing. Waiting for that very last particle to drop may not be the best approach. Bob Correct. Marking time with an hour glass is not that different from marking time with a 1PPS. Each signal has a rise time; one picks the appropriate live trigger level or sampled slope waveform model to minimize jitter. Waiting for the last grain is like waiting for the last millivolt of a TTL 1PPS pulse; no one does that. Note that [this] hourglass interval has a standard deviation on the order of 10 seconds. So my initial goal is 1 second timing resolution, which turns out to be pretty easy to do optically. Whether sand or cesium, phase comparators have a minimum resolution. While lower resolution is better, if the ADEV of the DUT is too far above the ADEV of the comparator then that resolution is wasted. So detection to a granularity of 1 second is sufficient for this application. /tvb ___ 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] nubie querie
Hi A clock and a hazmat site all rolled into one. Bob On Mar 5, 2010, at 2:41 PM, paul swed wrote: OK then if you ground up cesium azide and put it in the hour glass wouldn't you have a cesium clock at much lower cost (And accuracy) then an HP?? Might last quite a while also. On Fri, Mar 5, 2010 at 1:53 PM, Tom Van Baak t...@leapsecond.com wrote: Even defining when the sand timer is done is not a real simple thing. Waiting for that very last particle to drop may not be the best approach. Bob Correct. Marking time with an hour glass is not that different from marking time with a 1PPS. Each signal has a rise time; one picks the appropriate live trigger level or sampled slope waveform model to minimize jitter. Waiting for the last grain is like waiting for the last millivolt of a TTL 1PPS pulse; no one does that. Note that [this] hourglass interval has a standard deviation on the order of 10 seconds. So my initial goal is 1 second timing resolution, which turns out to be pretty easy to do optically. Whether sand or cesium, phase comparators have a minimum resolution. While lower resolution is better, if the ADEV of the DUT is too far above the ADEV of the comparator then that resolution is wasted. So detection to a granularity of 1 second is sufficient for this application. /tvb ___ 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] nubie querie
Plus the effect of a star quake when the crystalline crust rearranges itself. Somewhat analogous to a crystal jump. Bruce Bob Camp wrote: Hi Then there's the phase noise of the pulsar oscillator - For a simple crystal oscillator the two word answer might be Leeson's model. That of course is a cop out since it clearly defines multiple things that contribute to phase noise. Bob On Mar 5, 2010, at 9:39 AM, Richard (Rick) Karlquist wrote: Don Collie jnr wrote: I`m not sure that questions like these is welcome on this list, but here goes anyway : 1/ What are the the 10 sources of the most constant [invariant] frequencies known to man, in order of decreacing constancy? Four immediately come to mind. I vaguely remember reading that pulsars have some fantastic stability like 1E-20. I don't remember how they established this. 2/ What is the mechanism in an oscillator, that is responsible for phase noise? [In only one sentence please] Thermal (Johnson) noise in the resonator and thermal and shot noise in the active device. If this is known, then it becomes easier to design low phase noise oscillators. Perhaps, but just knowing the mechanism doesn't tell you that the phase noise is inversely proportional to loaded Q, which you would also need to know to optimize phase noise. I hope you enjoy these questions,.Don. ___ 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] nubie querie
Even defining when the sand timer is done is not a real simple thing. Waiting for that very last particle to drop may not be the best approach. Bob You could measure of the weight of the hourglass. Phil ___ 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] nubie querie
Eh, does the weight change if the sand runs from top to bottom? Some quantum mechanic effect I am missing? Or maybe a change in gravity as the sand drops from high to low? phil wrote: Even defining when the sand timer is done is not a real simple thing. Waiting for that very last particle to drop may not be the best approach. Bob You could measure of the weight of the hourglass. Phil ___ 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] nubie querie
Yes it does due to the variation of gravitational attraction between the object and the Earth with height above the ground. However this classical effect is very small and probably virtually impossible to measure. Bruce Gerard PG5G wrote: Eh, does the weight change if the sand runs from top to bottom? Some quantum mechanic effect I am missing? Or maybe a change in gravity as the sand drops from high to low? phil wrote: Even defining when the sand timer is done is not a real simple thing. Waiting for that very last particle to drop may not be the best approach. Bob You could measure of the weight of the hourglass. Phil ___ 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] nubie querie
Quoth Bruce Griffiths at 2010-03-06 07:58... Yes it does due to the variation of gravitational attraction between the object and the Earth with height above the ground. However this classical effect is very small and probably virtually impossible to measure. So, if the mass is closer to the centre of the planet, it weighs more? Never really considered this before, but fascinating nonetheless. Wonder if this would affect the moment of a pendulum. -- Matthew Smith Smiffytech - Technology Consulting Web Application Development Business: http://www.smiffytech.com/ Blog/personal: http://www.smiffysplace.com/ LinkedIn: http://www.linkedin.com/in/smiffy Skype: msmiffy Twitter: @smiffy ___ 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] nubie querie
Matthew Smith wrote: Quoth Bruce Griffiths at 2010-03-06 07:58... Yes it does due to the variation of gravitational attraction between the object and the Earth with height above the ground. However this classical effect is very small and probably virtually impossible to measure. So, if the mass is closer to the centre of the planet, it weighs more? Never really considered this before, but fascinating nonetheless. Wonder if this would affect the moment of a pendulum. For a spherical Earth with a spherically symmetric mass distribution the vertical gradient is around -0.3ppm/m. For the real Earth with the situation is somewhat more complex: http://gge.unb.ca/Personnel/Vanicek/MeanVerticalGradient.pdf The period of a pendulum will vary with its height above the terrain. 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] nubie querie
As one who has measured vague things like hourglass time to great accuracy, I would suggest finding a robust definition of end of flow. This would inevitably involve watching the flow past the end of flow to determine retrospectively when the flow had effectively ceased. To be fair to the hourglass you should at least use a caesium standard to keep time while this process occurs, you can then confidently correct the reversals of the hourglass for the turn-over dead time. It should make for a simple timer, cheers, Neville Michie ___ 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] nubie querie
On Sat, 06 Mar 2010 08:03:01 +1030, Matthew Smith wrote: So, if the mass is closer to the centre of the planet, it weighs more? Never really considered this before, but fascinating nonetheless. No! The gravitational attraction will decrease once penetrating the surface. At the center of gravity there should be no attraction anymore - the attraction will be the same to all directions summing to 0. What does the pendulum and the hour glass? Interesting, are there already some measurement results done in deep mines? Arnold ___ 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] nubie querie
Not to kick sand in your face, but it seems that in order for your automated turn-over device to work, as well as to accurately measure the time intervals, you would need a means to determine when the sand quits flowing. Correct. It's not unlike a zero crossing detector. The period of the sand flowing cycle is only 0.000278 Hz (1/hour). Possibly an accelerometer or microphone, with the added benefit of being able to hear the close-in phase noise. I wasn't planning on it but an optical detector sampled by a sound card might also give a pleasant audio signal as well as a data source from which the end-of-sand point can be determined with greater accuracy. I admire your dedication to monitoring the hour long periods of the sand timer so diligently. Truly a time-nut! You now all see why the hourglass is on top of the H-maser. Issues of installation, environment, reliability, instrumentation, gravity, data analysis, noise, stability and long-term frequency drift are very similar for both clocks. And given the sand inside, it's also a ... quartz crystal oscillator. /tvb ___ 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] nubie querie
It's all very well to talk about zero-crossing detection in an hour glass, but you haven't got an oscillator until you have some uniform means to flip it. Then you can talk about measuring the period (two flips) over some useful interval. Seems like the flip should take a second or so. Too fast and the glass breaks, too slow and you get sliding effects on the pile as it rotates. Tom says the deltas are around ten seconds, so whatever happens in one second doesn't much matter, as long as it is repeatable. Same thing with the crossing detector. You don't want much sand left in the upper glass, but you want it to be repeatable. Across the throat is probably OK, but you could put a led in the center of each end, and detect light scatter from the top on the bottom pile when enough sand runs out. Hmmm . . . This might be more interesting than the pendulum experiment that I never got to. Won't need expensive counters, either. Bill Hawkins ___ 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] nubie querie
Hi The best answer to the second one is That depends. There are *lots* of different oscillators out there. Earth - sun, Helium atom floating in space ... Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Don Collie jnr Sent: Thursday, March 04, 2010 8:14 AM To: time-nuts@febo.com Subject: [time-nuts] nubie querie I`m not sure that questions like these is welcome on this list, but here goes anyway : 1/ What are the the 10 sources of the most constant [invariant] frequencies known to man, in order of decreacing constancy? Four immediately come to mind. 2/ What is the mechanism in an oscillator, that is responsible for phase noise? [In only one sentence please] If this is known, then it becomes easier to design low phase noise oscillators. I hope you enjoy these questions,.Don. ___ 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] nubie querie
1/ There are no sources of constant frequency. Approximations to that goal may be measured by their cost. 2/ There is no single mechanism, unless it's quantum mechanics. Bill Hawkins This message has been fact checked by a 9 year old with a Twitter account. -Original Message- From: Bob Camp Sent: Thursday, March 04, 2010 11:05 AM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] nubie querie Hi The best answer to the second one is That depends. There are *lots* of different oscillators out there. Earth - sun, Helium atom floating in space ... Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Don Collie jnr Sent: Thursday, March 04, 2010 8:14 AM To: time-nuts@febo.com Subject: [time-nuts] nubie querie I`m not sure that questions like these is welcome on this list, but here goes anyway : 1/ What are the the 10 sources of the most constant [invariant] frequencies known to man, in order of decreacing constancy? Four immediately come to mind. 2/ What is the mechanism in an oscillator, that is responsible for phase noise? [In only one sentence please] If this is known, then it becomes easier to design low phase noise oscillators. I hope you enjoy these questions,.Don. ___ 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] nubie querie
I`m not sure that questions like these is welcome on this list, but here goes anyway : 1/ What are the the 10 sources of the most constant [invariant] frequencies known to man, in order of decreacing constancy? Four immediately come to mind. 2/ What is the mechanism in an oscillator, that is responsible for phase noise? [In only one sentence please] If this is known, then it becomes easier to design low phase noise oscillators. I hope you enjoy these questions,.Don. Don, See http://www.leapsecond.com/ten/ and http://www.leapsecond.com/ten/clock-powers-of-ten-tvb.pdf /tvb ___ 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] nubie querie
Hi Tom: In the last slide you show a sand timer. Do you have accuracy data for it? Have Fun, Brooke Clarke http://www.PRC68.com Tom Van Baak wrote: I`m not sure that questions like these is welcome on this list, but here goes anyway : 1/ What are the the 10 sources of the most constant [invariant] frequencies known to man, in order of decreacing constancy? Four immediately come to mind. 2/ What is the mechanism in an oscillator, that is responsible for phase noise? [In only one sentence please] If this is known, then it becomes easier to design low phase noise oscillators. I hope you enjoy these questions,.Don. Don, See http://www.leapsecond.com/ten/ and http://www.leapsecond.com/ten/clock-powers-of-ten-tvb.pdf /tvb ___ 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] nubie querie
In the last slide you show a sand timer. Do you have accuracy data for it? Hi Brooke, The past 3 hours the one hour timer measures 56:24, 56:19, and 56:30. That's at 67 F room temp. Somewhere I have enough clean data to compute the ADEV; it's more stable than accurate. It also has a tempco (one day when my wife wasn't looking I collected data inside the kitchen refrigerator, and oven). I would guess it has very little dependence on barometric pressure or humidity since all the sand is sealed inside the blown glass bulb. Eventually I will mechanically automate the hourly turn-over and get 24x7 long-term data. If I also model the tempco it may be possible to temperature compensate the rate error. I don't know where the flicker floor will be. My prediction is this hour-glass will gradually speed up as the glass or the sand slowly wear over time. /tvb ___ 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.
