Re: [time-nuts] Best reason
On Thu, Mar 29, 2012 at 08:43, Hal Murray hmur...@megapathdsl.net wrote: I think of GPS as a bunch of satellites broadcasting I'm Bob, my orbit parameters are XXX, my clock says YYY. If you hear 4 of those, you have 4 equations to work out 4 unknowns. The unknowns are your position: X, Y, Z, and T. But, but, but, they told you the value of Y three times. Why don't they say: I'm Bob, my orbit parameters are X,Y,Z, my clock says T. Nothing to solve :-) And GPS jamming would work by other people calling you with: Hi, Hal, ignore that guy, _I_ am the genuwine Bob. (For those who see this in a list archive many years from now: I am NOT serious, please). -- Sanjeev Gupta, the person formerly known as Bob +65 98551208 http://www.linkedin.com/in/ghane ___ 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] Best reason
I'm currently have to convince management that our 6-1/2 DMM (0.01% uncertainty) can't be used to test the 0.1ppm DC Source that we're repairing. Don't bother, just send it to me (once you've fixed it natch) :) On a more serious note what it this DC source that can manage 0.1ppm - the only thing I can think of that achieve that level of accuracy has to be a Josephson junction array. Dave ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Best reason
Yes, and moreover: what kind of test can be done on that DC source if no DMM is able to show that accuracy? On Thu, Mar 29, 2012 at 9:53 AM, David C. Partridge david.partri...@perdrix.co.uk wrote: I'm currently have to convince management that our 6-1/2 DMM (0.01% uncertainty) can't be used to test the 0.1ppm DC Source that we're repairing. Don't bother, just send it to me (once you've fixed it natch) :) On a more serious note what it this DC source that can manage 0.1ppm - the only thing I can think of that achieve that level of accuracy has to be a Josephson junction array. Dave ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Best reason
When I subscribed to Time Nuts several years ago I felt a little self-concise and purchased a Citizen WWV watch and in all seriousness it has run flawlessly. But I quickly learned that to really fit in I would need a tourbillon movement watch or the TVB mondo wrist watch demonstrated by a professional hand model in the Leapsecond site. Thomas Knox Date: Thu, 29 Mar 2012 21:20:14 +0200 From: att...@kinali.ch To: n1...@alum.dartmouth.org; time-nuts@febo.com Subject: Re: [time-nuts] Best reason On Wed, 28 Mar 2012 13:42:39 -0400 David McGaw n1...@alum.dartmouth.org wrote: Mechanical wristwatches are capable of good precision. I have an inexpensive 40-year old Caravelle (Bulova) that with reasonable adjustment can still keep to a few seconds per day. I never have considered quartz watches to be better unless they can be adjusted, which most cannot. Modern quarz watches use TCXOs and are calibrated. At least my Tissot keeps time to somewhere around 10-20s/half year. Attila Kinali -- Why does it take years to find the answers to the questions one should have asked long 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. ___ 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] Best reason
On Wed, 28 Mar 2012 19:28:20 +1100 Jim Palfreyman jim77...@gmail.com wrote: Why do we need really accurate clocks? Accurate clocks are expensive. The more money the US war machine spends for accurate clocks, the less money they have to build weapons. Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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] Best reason
In message calh-g5ygw4etqguifmo5czv1pxp3vhdhoyz9em6oa9_mvb4...@mail.gmail.com , Jim Palfreyman writes: So when a member of the general public says: Why do we need really accurate clocks? What is your answer? Because accurate clocks is the central technology that makes GPS, mobile phones and the internet work. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Best reason
Why do we need really accurate clocks? Time or frequency? p...@phk.freebsd.dk said: Because accurate clocks is the central technology that makes GPS, mobile phones and the internet work. What part of the internet depends upon accurate clocks? Ethernet, for example, requires roughly similar frequencies but doesn't care at all about time. -- 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] Best reason
On 3/28/12 1:28 AM, Jim Palfreyman wrote: So when a member of the general public says: Why do we need really accurate clocks? What is your answer? Personally I explain that accurate clocks enable you to pack a higher data rate into your smart phone. They like that. But I don't know that it's actually true. The phone application has to tolerate temperature swings, and the modulation needs to be suitable for a multipath environment, but timing isn't as important. Some degree of timing is needed for time difference of arrival kinds of position finding for E-911, although these days, I think more of that is assisted GPS, and in any case, the timing requirement to get 100 meter-ish precision isn't all that tight. Any other thoughts? Precision navigation. Not just GPS in your car, but things like: pesticide, fertilizer, and seed application better grading for roads and construction repeat pass interferometric radar (allows much better remote sensing from airborne platforms, which is cheaper than stomping through the bushes and weeds) disaster management aircraft routing and landing 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. ___ 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] Best reason
Usually (and unfortunately) governments tend to gather more money from tax rather than giving up something (Italy docet). On Wed, Mar 28, 2012 at 11:39 AM, Attila Kinali att...@kinali.ch wrote: On Wed, 28 Mar 2012 19:28:20 +1100 Jim Palfreyman jim77...@gmail.com wrote: Why do we need really accurate clocks? Accurate clocks are expensive. The more money the US war machine spends for accurate clocks, the less money they have to build weapons. Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ 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] Best reason
In message 20120328113122.5c868800...@ip-64-139-1-69.sjc.megapath.net, Hal Mu rray writes: Because accurate clocks is the central technology that makes GPS, mobile phones and the internet work. What part of the internet depends upon accurate clocks? SONET at the bottom and eBay endings at the top and a lot of stuff in the middle. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Best reason
On 3/28/12 1:28 AM, Jim Palfreyman wrote: So when a member of the general public says: Why do we need really accurate clocks? Not necessarily at time-nuts performance, but here's some clock and clock distribution applications There are a lot of systems out there that timestamp something going in, and somewhere else, it gets timestamped going out, and the difference determines how much you pay. Parking lots are a good example. You need to have all the timeclocks synchronized, so that people are charged the right amount Automated speeding ticket generators on tollways compare timestamps of passage through the toll station with measured distance to determine average speed. === What's interesting is that a lot of things inherently depend on ppm kinds of timing accuracy that you wouldn't expect.. 10ppm is 1 second per day drift, and most inexpensive quartz oscillators aren't that good. 50-100 ppm is more typical. While 1 second isn't a big deal, but 30 seconds over a month might be, and 5 minutes in a month is a problem (you'd hate it if your DVR started recording your program 30 seconds after it started) ___ 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] Best reason
Well the best reason is that by our social convention it makes people comfortable. But that reason does have much logic behind it. ___ 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] Best reason
There are good technical reasons for having very accurate standards of time interval, but IMO, far fewer reasons for ns or even ms accuracy in time of day. Most everyday things, except possibly eBay and some financial transactions, really don't have to happen exactly on the dot. As to having very accurate time, widely distributed, and then measuring time interval by subtraction, that is fraught with perils. Would you use a the difference between a pair of mile long platinum-iridium rods to measure the thickness of a sheet of paper? YMMV, -John Well the best reason is that by our social convention it makes people comfortable. But that reason does have much logic behind it. ___ 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] Best reason
batchelo...@yahoo.com wrote Well the best reason is that by our social convention it makes people comfortable. But that reason does have much logic behind it. One month ago a 38-year old wristwatch resurfaced from a junk box and I decided to return to it at least temporarily. It drifts some 30 seconds per day, but sincerely I don't feel any particular discomfort with it. Antonio I8IOV ___ 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] Best reason
Mechanical wristwatches are capable of good precision. I have an inexpensive 40-year old Caravelle (Bulova) that with reasonable adjustment can still keep to a few seconds per day. I never have considered quartz watches to be better unless they can be adjusted, which most cannot. David On 3/28/12 1:08 PM, iov...@inwind.it wrote: batchelo...@yahoo.com wrote Well the best reason is that by our social convention it makes people comfortable. But that reason does have much logic behind it. One month ago a 38-year old wristwatch resurfaced from a junk box and I decided to return to it at least temporarily. It drifts some 30 seconds per day, but sincerely I don't feel any particular discomfort with it. Antonio I8IOV ___ time-nuts mailing list --time-nuts@febo.com To unsubscribe, go tohttps://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] Best reason
Two good reasons: (1) Many uses in science and engineering. Mostly indirectly, you need a good frequency standard to calibrate some instrument so you can measure something. Thinks like distance, current, capacitance are based on time if you follow the chain long enough.As frequencies get lower you starting thinking of period and so now you need to know the time.There are many practical reasons but most are many levels indirect. (2) it is a fun hobby, like building a model ship inside a glass bottle it is useless but that is the point of hobbies. ___ 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] Best reason
On 3/28/2012 1:42 PM, David McGaw wrote: I never have considered quartz watches to be better unless they can be adjusted, which most cannot. Most decent ones can be. I've got some Citizens and Seikos, which have a small trimmer cap you can adjust. There's usually a test point nearby with a easy to figure out frequency output you can look at with a good counter (I think I've seen both 100 Hz and 32768 Hz outputs). ___ 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] Best reason
Antonio I8IOV wrote: I wrote: Well the best reason is that by our social convention it makes people comfortable. But that reason does have much logic behind it. One month ago a 38-year old wristwatch resurfaced from a junk box and I decided to return to it at least temporarily. It drifts some 30 seconds per day, but sincerely I don't feel any particular discomfort with it. Obviously I meant to say that it doesn't have much logic, not that it does have much logic. Clearly for tens of thousands of years we had no more precision than daily sunrise for timekeeping, so the world won't vanish if we don't have accurate clocks. I myself have a few mechanical watches, and I no longer wear a wrist watch since I seem to be surrounded by clocks all the time. Every computer screen in my sight has the TOD in the corner. My cell phone has the TOD. There's a clock on the wall in almost every room I walk in at work and at home. But our social convention has changed over time, and now we expect to know the time precision closer than sunrise/sunset can tell us. Personally, +/- a minute or two is good enough for most everything I do in my life. But frequency is important to me. Michael / KA7ZNZ ___ 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] Best reason
1 nanosecond = 1 foot, do you know where you are? Remember, wherever you go, there you are. Buckaroo Banzai On 3/28/2012 3:28 AM, Jim Palfreyman wrote: So when a member of the general public says: Why do we need really accurate clocks? What is your answer? Personally I explain that accurate clocks enable you to pack a higher data rate into your smart phone. They like that. Any other thoughts? 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. ___ 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] Best reason
jim77...@gmail.com said: So when a member of the general public says: Why do we need really accurate clocks? What is your answer? Personally I explain that accurate clocks enable you to pack a higher data rate into your smart phone. They like that. Any other thoughts? Navigation? It goes back to Harrison. Dava Sobel's Longitude is good. There is a version with nice pictures. GPS is probably something they can appreciate. If you have to explain why GPS needs accurate clocks, it might be simpler to start with LORAN in 2D. Work out a simple example and then do it again with one of the transmitters being off by a few microseconds. I think of GPS as a bunch of satellites broadcasting I'm Bob, my orbit parameters are XXX, my clock says YYY. If you hear 4 of those, you have 4 equations to work out 4 unknowns. The unknowns are your position: X, Y, Z, and T. -- 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] Best reason
jim77...@gmail.com said: So when a member of the general public says: Why do we need really accurate clocks? What is your answer? The alternative is inaccurate clocks, would that ever be preferable? ___ 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] Best reason
Hi All, Thanks Jim P for the thread. I was lurking hoping for some amazing idea that would help me explain (in simple and interesting terms) what I do, firstly you need to know my company is the local rep for Symmetricom in Australia. So when asked what I do for a living, you should see the eyes glaze over; so normally easier to just say no you first! I thought this thread was going to be my saviour! Sadly not to be. lol Chris -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Stake Sent: Thursday, 29 March 2012 12:31 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Best reason jim77...@gmail.com said: So when a member of the general public says: Why do we need really accurate clocks? What is your answer? The alternative is inaccurate clocks, would that ever be preferable? ___ 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] Best reason
People can all relate to their cellphones. Just tell them that the cellphones all yell at each other but not at the same time so as long as you know when to listen you can hear the other end. :-) Regards Randall -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Dawes Sent: Thursday, 29 March 2012 2:41 p.m. To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Best reason Hi All, Thanks Jim P for the thread. I was lurking hoping for some amazing idea that would help me explain (in simple and interesting terms) what I do, firstly you need to know my company is the local rep for Symmetricom in Australia. So when asked what I do for a living, you should see the eyes glaze over; so normally easier to just say no you first! I thought this thread was going to be my saviour! Sadly not to be. lol Chris -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Stake Sent: Thursday, 29 March 2012 12:31 PM To: 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Best reason jim77...@gmail.com said: So when a member of the general public says: Why do we need really accurate clocks? What is your answer? The alternative is inaccurate clocks, would that ever be preferable? ___ 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] Best reason
Just remember, to the 'average' person (no such exists in reality), all technology is magic. The TV remote is a magic wand that you wave at the TV and recite the proper incantation (sometimes profane). You chant the spell to your smart phone and you can talk to your friend anywhere in the world. Everyone knows the 'spells' to make things operate, but have no idea how they actually work. The math used with GPS is beyond most (non-technical) college graduates. One young child was asked how TV worked and he answered 'with gas. The pipe (cable) bring the picture in and the electricity heats it up to fill the screen'. He knew that things expand when heated and made the connection. This (6 or 7 year old, if I recall) showed far more scientific reasoning than most of our elected officials. Most people understand faster, slower, bigger, smaller, but 'more accurate' is a hard concept. 1% accuracy is bad until you realize you are referring 1% uncertainty (99% accuracy). I'm currently have to convince management that our 6-1/2 DMM (0.01% uncertainty) can't be used to test the 0.1ppm DC Source that we're repairing. My earlier comment of '1 nanosecond = 1 foot' really applies to GPS. If the atomic clock on the satellites are allowed to drift, even a fraction of a nanosecond, the accuracy of the whole system quickly degrades. These clocks are updated at less than 4 hour intervals to keep this from happening. Mike On 3/28/2012 7:43 PM, Hal Murray wrote: jim77...@gmail.com said: So when a member of the general public says: Why do we need really accurate clocks? What is your answer? Personally I explain that accurate clocks enable you to pack a higher data rate into your smart phone. They like that. Any other thoughts? Navigation? It goes back to Harrison. Dava Sobel's Longitude is good. There is a version with nice pictures. GPS is probably something they can appreciate. If you have to explain why GPS needs accurate clocks, it might be simpler to start with LORAN in 2D. Work out a simple example and then do it again with one of the transmitters being off by a few microseconds. I think of GPS as a bunch of satellites broadcasting I'm Bob, my orbit parameters are XXX, my clock says YYY. If you hear 4 of those, you have 4 equations to work out 4 unknowns. The unknowns are your position: X, Y, Z, and T. ___ 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] Best reason
jim77...@gmail.com said: So when a member of the general public says: Why do we need really accurate clocks? What is your answer? The alternative is inaccurate clocks, would that ever be preferable? Wouldn't that depend on how late for work you were? ___ 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.
