Re: [time-nuts] Mechanical 1PPS Oscillator Disciplining
Wow! That reference is a nugget of pure gold amongst the chaff. As a mechanical engineer by training (BSME MIT 1960) and experience (industrial process control), I am deeply interested in electromechanical things. Experience suggests that it is impossible for widely separated pendulum clocks to remain synched with each other indefinitely. RS-232 communication does not require synchronized clocks because the message contains a string of bits that synchronizes the clocks adequately before the message begins. Certainly computer crystal clocks are not synchronized. Is it true that there have been no new ideas since the turn of the century? Sadly, there seems to be some hype in Stephenson's beautifully written article. On New Year's Day as I set a Seth Thomas pendulum clock that has been running for over a hundred years, I thought about disciplining a 10 MHz oscillator with the pendulum's beat in order to measure the variations in ADEV and phase noise through the seasons. I have some of the older Lucent boxes (with Rb) that could be modified to provide the PCDO (pendulum clock), but I don't know what I need to calculate and record those measurements. For that matter, is it feasible or is there too much noise? Am I the 420,000th person to try this? Any answers appreciated. Bill Hawkins -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Andy Bardagjy Sent: Friday, January 09, 2015 11:22 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] Mechanical 1PPS Oscillator Disciplining From a fascinating (albeit long) article about transatlantic communication cables http://archive.wired.com/wired/archive/4.12/ffglass.html On the bottom of page 45 to the top of page 46 Each piece of equipment on this tabletop is built around a motor that turns over at the same precise frequency. None of it would work - no device could communicate with any other device - unless all of those motors were spinning in lockstep with one another. The transmitter, regenerator/retransmitter, and printer all had to be in sync even though they were thousands of miles apart. This feat is achieved by means of a collection of extremely precise analog machinery. The heart of the system is another polished box that contains a vibrating reed, electromagnetically driven, thrumming along at 30 cycles per second, generating the clock pulses that keep all the other machines turning over at the right pace. The reed is as precise as such a thing can be, but over time it is bound to drift and get out of sync with the other vibrating reeds in the other stations. In order to control this tendency, a pair of identical pendulum clocks hang next to each other on the wall above. These clocks feed steady, one-second timing pulses into the box housing the reed. The reed, in turn, is driving a motor that is geared so that it should turn over at one revolution per second, generating a pulse with each revolution. If the frequency of the reed's vibration begins to drift, the motor's speed will drift along with it, and the pulse will come a bit too early or a bit too late. But these pulses are being compared with the steady one-second pulses generated by the double pendulum clock, and any difference between them is detected by a feedback system that can slightly speed up or slow down the vibration of the reed in order to correct the error. The result is a clock so steady that once one of them is set up in, say, London, and another is set up in, say, Cape Town, the machinery in those two cities will remain synched with each other indefinitely. Does anyone know any other history about that particular piece of equipment? Cheers! Andy ? Bardagjy.com ? +1-404-964-1641 ___ 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] Mechanical 1PPS Oscillator Disciplining
Alex, Now it's time to share some of my favorite vintage time frequency links. Some very nice vintage low frequency quartz crystals (20 kHz down to 5 kHz): http://www.cdvandt.org/luminous_quartz.htm Lothar Rohde's revolutionary portable quartz-clock type: CFQ http://www.cdvandt.org/CFQ.pdf http://www.cdvandt.org/cfq.htm Quartz-clock designed by the “PTR”, Germany’s Bureau of Standard, in the 1920s and 1930s http://www.cdvandt.org/PTR%20quartz-clock.pdf http://www.cdvandt.org/ptr_quartz-clock.htm A British technical report on German Quartz Clocks: http://www.cdvandt.org/BIOS-1316.pdf The above ~10 page PDF is a must-read for any of you interested in the early history of quartz timekeeping. Note one of the authors was Louis Essen, who went on to develop the first cesium clock, the guy behind the 9192631770 Hz cesium definition of the second, and one of the first to propose leap seconds. I have more Essen info here: http://leapsecond.com/history For that matter, if you have time, the entire German History of Technology web site is fascinating: http://www.cdvandt.org/ /tvb - Original Message - From: Alex Pummer a...@pcscons.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, January 09, 2015 3:27 PM Subject: Re: [time-nuts] Mechanical 1PPS Oscillator Disciplining yes, Ulrich's [ Rohde ] Father made a high precision clock around 1940, which had an electronically tuned mechanical oscillator. The vibrating 400Hz tuning fork is phase locked to a quartz crystal oscillator, that was the most precise clock at that time, and it worked as I have seen it at the company as I worked there in the sixties of the past century. 73 KJ6UHN Alex ___ 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] Mechanical 1PPS Oscillator Disciplining
Hi Tom dividing down wasn't always necessary I have sample from the UK GPO Crystal Factory of NT-cut bars, quartz tuning fork, and Gapped Ring crystals, the latter marked 400cps (pre Hertz :-)) ) I think these are post WWII because they are mounted in IO base GT style tube envelopes. Dividers were achieved with neons and locked multivibrators, where necessary, I believe. [] Alan G3NYK I have one 500 c/s GEC crystal in an octal base which is thinner than a 60 Kc/s one, so a different mode. Never had it working, though. 73, David GM8ARV -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ 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] Mechanical 1PPS Oscillator Disciplining
Hi The speed of sound in quartz varies by axis, but only by about 2:1. The same basic physics that gets you a fundamental 5 MHz crystal that is at thickness Z gives you some dimension on a 5 KHz crystal that’s close to 1000 * Z. Very low frequency crystals pretty much have to be designed so they resonate on a “long” axis of the blank. If they don’t then the blank / enclosure / price gets crazy big. If you want to calculate just how long this or that resonance might be: http://www.mt-berlin.com/frames_ao/descriptions/sio2.htm Has all the numbers you would need. Bob On Jan 10, 2015, at 2:06 AM, David J Taylor david-tay...@blueyonder.co.uk wrote: Hi Tom dividing down wasn't always necessary I have sample from the UK GPO Crystal Factory of NT-cut bars, quartz tuning fork, and Gapped Ring crystals, the latter marked 400cps (pre Hertz :-)) ) I think these are post WWII because they are mounted in IO base GT style tube envelopes. Dividers were achieved with neons and locked multivibrators, where necessary, I believe. [] Alan G3NYK I have one 500 c/s GEC crystal in an octal base which is thinner than a 60 Kc/s one, so a different mode. Never had it working, though. 73, David GM8ARV -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ 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] Mechanical 1PPS Oscillator Disciplining
Hi David yes I think I have seen similar but not as low as that. If you compare the suspension points the different vibrational mode should obvious.the suspension point is at a node. I think some of these are quite difficult to excite, I have not seen any suggested circuits but I have not looked too hard. Alan - Original Message - From: David J Taylor david-tay...@blueyonder.co.uk To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Saturday, January 10, 2015 7:06 AM Subject: Re: [time-nuts] Mechanical 1PPS Oscillator Disciplining Hi Tom dividing down wasn't always necessary I have sample from the UK GPO Crystal Factory of NT-cut bars, quartz tuning fork, and Gapped Ring crystals, the latter marked 400cps (pre Hertz :-)) ) I think these are post WWII because they are mounted in IO base GT style tube envelopes. Dividers were achieved with neons and locked multivibrators, where necessary, I believe. [] Alan G3NYK I have one 500 c/s GEC crystal in an octal base which is thinner than a 60 Kc/s one, so a different mode. Never had it working, though. 73, David GM8ARV -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ 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] Mechanical 1PPS Oscillator Disciplining
Similarly, the Tektronix 647 oscilloscope, uses a 4KHz quartz crystal oscillator, divided by 4 to form its 1KHz calibrator signal. You can hear the crystal resonate whenever the calibrator is turned on. The crystal is mounted in an elongated, hermetically sealed, HC7 style can. -Chuck Harris David J Taylor wrote: Hi Tom dividing down wasn't always necessary I have sample from the UK GPO Crystal Factory of NT-cut bars, quartz tuning fork, and Gapped Ring crystals, the latter marked 400cps (pre Hertz :-)) ) I think these are post WWII because they are mounted in IO base GT style tube envelopes. Dividers were achieved with neons and locked multivibrators, where necessary, I believe. [] Alan G3NYK I have one 500 c/s GEC crystal in an octal base which is thinner than a 60 Kc/s one, so a different mode. Never had it working, though. 73, David GM8ARV ___ 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] Mechanical 1PPS Oscillator Disciplining
Hi The mounting points are the standard locations for a flexure bar running the resonance along it’s length. The sandwich blank is a bit unique. The normal gate feedback style circuits will get the crystal running. The impedance will be quite high, so you will need a bit of gain. At low frequencies, a CMOS input op-amp will do the trick. Bob On Jan 10, 2015, at 12:24 PM, David J Taylor david-tay...@blueyonder.co.uk wrote: Hi David yes I think I have seen similar but not as low as that. If you compare the suspension points the different vibrational mode should obvious.the suspension point is at a node. I think some of these are quite difficult to excite, I have not seen any suggested circuits but I have not looked too hard. Alan I uploaded a couple of pictures taken with the 'phone. http://www.satsignal.eu/Radio/2015-01-10-1700-54-crop.jpg http://www.satsignal.eu/Radio/2015-01-10-1702-51-crop.jpg The first photo shows the size and mounting points of the crystal. The crystal itself appears to be a two-layer structure. The second photo shows a detail of one of the mounting points. The gold plating appears to have been scraped away at the edge, and some sort of solder join made at the edge. I might be able to do a better image with a different camera, but I don't know. Hope that is of some interest. David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ 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] Mechanical 1PPS Oscillator Disciplining
Hi David yes I think I have seen similar but not as low as that. If you compare the suspension points the different vibrational mode should obvious.the suspension point is at a node. I think some of these are quite difficult to excite, I have not seen any suggested circuits but I have not looked too hard. Alan I uploaded a couple of pictures taken with the 'phone. http://www.satsignal.eu/Radio/2015-01-10-1700-54-crop.jpg http://www.satsignal.eu/Radio/2015-01-10-1702-51-crop.jpg The first photo shows the size and mounting points of the crystal. The crystal itself appears to be a two-layer structure. The second photo shows a detail of one of the mounting points. The gold plating appears to have been scraped away at the edge, and some sort of solder join made at the edge. I might be able to do a better image with a different camera, but I don't know. Hope that is of some interest. David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ 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] Mechanical 1PPS Oscillator Disciplining
Back in about 1962 I joined a government research lab. My boss had bought a HP voltmeter (I remember it as being about a yard cubed) and a HP printer (also a yard cubed) and it printed out on 2 inch wide paper, like a cash register record. My boss's problem was that he wanted more precision in measuring a time dependent process. My problem was to trigger the voltmeter/printer to sample at exact intervals of time. I found a tuning fork standard (might have been GR) of 400 hertz, so a I built a divider using neon Dekatrons. These had ten electrodes in a circle visible from the end, and subsidiary electrodes would steer the glow to the next electrode when the tube was triggered. Each of these anodes must have had a separate load resistor, because I found each one had a voltage drop when it was illuminated. I used this with rotary selector switches to select divide integers by using the anode pulse to trigger a monostable (12AX7 ) to reset the Dekatron to zero and start counting again. We did not have logic circuits in those days, this was known as Pulse Techniques as used in military radar, which is where I got much of my early education. I have forgotten the voltmeter resolution it might have only been 4, 5, or 6 digits, but the data from the paper tape was then hand typed into an IBM card punch and the cards were couriered to head office to be fed into the main frame (probably IBM) We have come a long way in data acquisition and computing since then. 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] Mechanical 1PPS Oscillator Disciplining
Hi: You can see the 4 nodes on the Chinese Spouting bowl in my video at: https://www.youtube.com/watch?v=k68w3OrPztE When I got it from Cliff Stoll he had recommended using a wet towel to keep the bowl from moving but that damped the vibrations. I got 4 stick-on feet and placed them at the nodes seen in the video above and it works great. If the bowl is supported anywhere but the nodes the oscillations are damped, just like for a crystal. http://www.ted.com/talks/clifford_stoll_on_everything https://en.wikipedia.org/wiki/Clifford_Stoll http://www.kleinbottle.com/ - it looks like he no longer carries the spouting bowl. Mail_Attachment -- Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Bob Camp wrote: Hi The mounting points are the standard locations for a flexure bar running the resonance along it’s length. The sandwich blank is a bit unique. The normal gate feedback style circuits will get the crystal running. The impedance will be quite high, so you will need a bit of gain. At low frequencies, a CMOS input op-amp will do the trick. Bob On Jan 10, 2015, at 12:24 PM, David J Taylor david-tay...@blueyonder.co.uk wrote: Hi David yes I think I have seen similar but not as low as that. If you compare the suspension points the different vibrational mode should obvious.the suspension point is at a node. I think some of these are quite difficult to excite, I have not seen any suggested circuits but I have not looked too hard. Alan I uploaded a couple of pictures taken with the 'phone. http://www.satsignal.eu/Radio/2015-01-10-1700-54-crop.jpg http://www.satsignal.eu/Radio/2015-01-10-1702-51-crop.jpg The first photo shows the size and mounting points of the crystal. The crystal itself appears to be a two-layer structure. The second photo shows a detail of one of the mounting points. The gold plating appears to have been scraped away at the edge, and some sort of solder join made at the edge. I might be able to do a better image with a different camera, but I don't know. Hope that is of some interest. David -- SatSignal Software - Quality software written to your requirements Web: http://www.satsignal.eu Email: david-tay...@blueyonder.co.uk ___ 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] Mechanical 1PPS Oscillator Disciplining
hol...@hotmail.com said: Basically the solenoid nudged the pendulum There was an article in Scientific American many years ago. They used a magnet mounted on the end of a stick attached to the pendulum arm. The arc of the magnet swung through a hole in the middle of a solenoid coil. A pulse on the coil at the right time provided the nudge with no physical contact. -- These are my opinions. 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.
[time-nuts] Mechanical 1PPS Oscillator Disciplining
Many years ago I built a GPSDPO (GPS Disciplined Pendulum Oscillator). A friend of mine inherited a grandfather clock built in the late 1700's. She had the movement cleaned and serviced and got the clock working fairly well, but it was not all that accurate. I built up a device using a GPS with 1PPS output, a PIC, an optical sensor, and a solenoid. Basically the solenoid nudged the pendulum and kept the clock spot on. I was expecting to have all sorts of problems figuring out where, when, and how much to nudge the pendulum, but it pretty much worked the first time. One major difficulty was the pendulum did not swing at 1 Hz. I seem to remember it was 48 (or 72?) swings/minute. ___ 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] Mechanical 1PPS Oscillator Disciplining
On 1/10/15 3:08 PM, Hal Murray wrote: hol...@hotmail.com said: Basically the solenoid nudged the pendulum There was an article in Scientific American many years ago. They used a magnet mounted on the end of a stick attached to the pendulum arm. The arc of the magnet swung through a hole in the middle of a solenoid coil. A pulse on the coil at the right time provided the nudge with no physical contact. or a coil under the pendulum bob, which is ferrous, a technique used in some large Foucault pendulums I didn't realize you can actually buy them as a sort of catalog item.. http://www.academypendulums.com/ They put the drive at the top. The most fascinating thing is the list of 122 pendulums they've installed http://www.academypendulums.com/foucault-pendulum-displays.html and some of the places they are.. there's a goodly number of museums, of course, but some other things..Wineries, Banks, Malls? the one in the Smithsonian was removed some years ago.. Very simple design the schematic (and the user manual including tuning instructions) is on the website under manuals Just a photodetector driving a solenoid, which apparently draws 300 mA from a 120VAC line. I haven't found details on the coil or armature design, but plenty of pictures. ___ 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] Mechanical 1PPS Oscillator Disciplining
Science Madness has a PDF of the book - Projects for the Amateur Scientist by SciAm columnist C.L. Stong. The pendulum is on page 290 http://www.sciencemadness.org/library/books/projects_for_the_amateur_scienti st.pdf Dave -Original Message- From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Hal Murray Sent: Saturday, January 10, 2015 15:09 To: Discussion of precise time and frequency measurement Cc: hmur...@megapathdsl.net Subject: Re: [time-nuts] Mechanical 1PPS Oscillator Disciplining hol...@hotmail.com said: Basically the solenoid nudged the pendulum There was an article in Scientific American many years ago. They used a magnet mounted on the end of a stick attached to the pendulum arm. The arc of the magnet swung through a hole in the middle of a solenoid coil. A pulse on the coil at the right time provided the nudge with no physical contact. -- These are my opinions. 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. ___ 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] Mechanical 1PPS Oscillator Disciplining
Hi Tom dividing down wasn't always necessary I have sample from the UK GPO Crystal Factory of NT-cut bars, quartz tuning fork, and Gapped Ring crystals, the latter marked 400cps (pre Hertz :-)) ) I think these are post WWII because they are mounted in IO base GT style tube envelopes. Dividers were achieved with neons and locked multivibrators, where necessary, I believe. The original ( 1926 ) frequency source for Rugby GBR 16kHz radio station was an invar tuning fork with a tube maintaining amplifier. I cannot find any information on syntonising that but it probably was not necessary. Alan G3NYK - Original Message - From: Tom Van Baak t...@leapsecond.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, January 09, 2015 9:51 PM Subject: Re: [time-nuts] Mechanical 1PPS Oscillator Disciplining Andy, Yes, Neal Stephenson's Mother Earth Mother Board article is a classic that every time nut should read at some point. The one page version is at http://archive.wired.com/wired/archive/4.12/ffglass_pr.html Prior to quartz, pendulum clocks and tuning fork oscillators were the standard. Even until the 1950's or early 1960's tuning fork oscillators were used when one needed accurate frequency in the audio range. That's because dividing down high frequency quartz oscillators to, say, 60 Hz or 400 Hz required lots of circuitry. Not sure if Neal's reference to vibrating reed is what we would call a tuning fork, or if it's something else. Here in the US General Radio made precision tuning fork oscillators. Model numbers 213, 723, 813, 815. One example is at http://leapsecond.com/museum/gr815b/ Also check out old issues of General Radio Experimenter magazine for details on these wonderful instruments. Pendulum clocks were also used in power plants around the world to keep the grid synchronized. There is occasional discussion about this on clock collecting or horology forums. They are precious and can be extremely accurate, as good as a second a year. Since pendulum clocks were better long-term timekeepers and generated only 0.5 or 1 Hz signals, a PDTF (Pendulum Disciplined Tuning Fork) made sense. Has a nice ring to it, doesn't it. /tvb - Original Message - From: Andy Bardagjy a...@bardagjy.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, January 09, 2015 9:22 AM Subject: [time-nuts] Mechanical 1PPS Oscillator Disciplining From a fascinating (albeit long) article about transatlantic communication cables http://archive.wired.com/wired/archive/4.12/ffglass.html On the bottom of page 45 to the top of page 46 Each piece of equipment on this tabletop is built around a motor that turns over at the same precise frequency. None of it would work - no device could communicate with any other device - unless all of those motors were spinning in lockstep with one another. The transmitter, regenerator/retransmitter, and printer all had to be in sync even though they were thousands of miles apart. This feat is achieved by means of a collection of extremely precise analog machinery. The heart of the system is another polished box that contains a vibrating reed, electromagnetically driven, thrumming along at 30 cycles per second, generating the clock pulses that keep all the other machines turning over at the right pace. The reed is as precise as such a thing can be, but over time it is bound to drift and get out of sync with the other vibrating reeds in the other stations. In order to control this tendency, a pair of identical pendulum clocks hang next to each other on the wall above. These clocks feed steady, one-second timing pulses into the box housing the reed. The reed, in turn, is driving a motor that is geared so that it should turn over at one revolution per second, generating a pulse with each revolution. If the frequency of the reed's vibration begins to drift, the motor's speed will drift along with it, and the pulse will come a bit too early or a bit too late. But these pulses are being compared with the steady one-second pulses generated by the double pendulum clock, and any difference between them is detected by a feedback system that can slightly speed up or slow down the vibration of the reed in order to correct the error. The result is a clock so steady that once one of them is set up in, say, London, and another is set up in, say, Cape Town, the machinery in those two cities will remain synched with each other indefinitely. Does anyone know any other history about that particular piece of equipment? Cheers! Andy ◉ Bardagjy.com ◉ +1-404-964-1641 ___ 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
Re: [time-nuts] Mechanical 1PPS Oscillator Disciplining
yes, Ulrich's [ Rohde ] Father made a high precision clock around 1940, which had an electronically tuned mechanical oscillator. The vibrating 400Hz tuning fork is phase locked to a quartz crystal oscillator, that was the most precise clock at that time, and it worked as I have seen it at the company as I worked there in the sixties of the past century. 73 KJ6UHN Alex On 1/9/2015 9:22 AM, Andy Bardagjy wrote: From a fascinating (albeit long) article about transatlantic communication cables http://archive.wired.com/wired/archive/4.12/ffglass.html On the bottom of page 45 to the top of page 46 Each piece of equipment on this tabletop is built around a motor that turns over at the same precise frequency. None of it would work - no device could communicate with any other device - unless all of those motors were spinning in lockstep with one another. The transmitter, regenerator/retransmitter, and printer all had to be in sync even though they were thousands of miles apart. This feat is achieved by means of a collection of extremely precise analog machinery. The heart of the system is another polished box that contains a vibrating reed, electromagnetically driven, thrumming along at 30 cycles per second, generating the clock pulses that keep all the other machines turning over at the right pace. The reed is as precise as such a thing can be, but over time it is bound to drift and get out of sync with the other vibrating reeds in the other stations. In order to control this tendency, a pair of identical pendulum clocks hang next to each other on the wall above. These clocks feed steady, one-second timing pulses into the box housing the reed. The reed, in turn, is driving a motor that is geared so that it should turn over at one revolution per second, generating a pulse with each revolution. If the frequency of the reed's vibration begins to drift, the motor's speed will drift along with it, and the pulse will come a bit too early or a bit too late. But these pulses are being compared with the steady one-second pulses generated by the double pendulum clock, and any difference between them is detected by a feedback system that can slightly speed up or slow down the vibration of the reed in order to correct the error. The result is a clock so steady that once one of them is set up in, say, London, and another is set up in, say, Cape Town, the machinery in those two cities will remain synched with each other indefinitely. Does anyone know any other history about that particular piece of equipment? Cheers! Andy ◉ Bardagjy.com ◉ +1-404-964-1641 ___ 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] Mechanical 1PPS Oscillator Disciplining
In message df7c7705-b1cc-4b8d-8bac-d471e2ab5...@bardagjy.com, Andy Bardagjy w rites: Does anyone know any other history about that particular piece of equipment? I seriously doubt those claims of precision. At datamuseum.dk we did a small booklet about the history of paper tape as a storage medium some years back, and the Great Nordic Telegraph Company was roughly half of the material. The first thing to notice is that most cables were simplex, you could only transmit in one direction at a time. The turnaround was suprisingly slow. Because of the dielectric absorption in many miles of cable you had to disconnect your (relatively high voltage) transmitter, short the cable for some time, before you could attach your (incredibly) sensitive receiver to the cable. Some time depended on cable type and length of cable, but up to five minutes were not unheard of. (The exact duration were often determined by the clerk putting his moistened finger across the terminal.) Needless to say this made it a paramount matter of efficiency to minimize turn-arounds, and therefore the general scheme of operation was that one side would transmit until they had cleared their backlog or until a certain maximum amount of time since last turnaround had elapsed. Some high-traffic cables ran on clockwork (minutes 0-15,30-45 A to B, minutes 15-30,45-00 B to A) -- this made it possible to predict how much papertape would be required. During each turning, the transmitter would be driven by papertape, each roll as large as physically practical, but there would still be a gap between individual messages on the tape and a longer gap between tapes. It was not uncommen for a high speed relay station to go through five miles of papertape a day at rates of several inches per second. This is even more astonishing when you realize that many of these relay stations were remotely situatated, like for instance the Eastern South African Telegraph Companys station on the island Bawe outside Zanzibar. For particular long cables repeater stations were necessary and since they only had two cables, there were never any doubt where the messages would go. Most, but not all of these skipped the paper-tape step, and had the receiving undulator drive the transmit relay directly. This is likely the kind of syncronized table described in the text. The majority of stations had more than two cables and therefore needed to make routing decisions, but messages would be batched as early as possible to minimize the number of paper tape splices required. Anyway... What all this boils down to is that the syntonization requirements were nowhere as dramatic as that text claims: +/- 5% were a very common specification. Driving the 30Hz reed with a pendulum clock would trivially do this. -- 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] Mechanical 1PPS Oscillator Disciplining
Andy, Yes, Neal Stephenson's Mother Earth Mother Board article is a classic that every time nut should read at some point. The one page version is at http://archive.wired.com/wired/archive/4.12/ffglass_pr.html Prior to quartz, pendulum clocks and tuning fork oscillators were the standard. Even until the 1950's or early 1960's tuning fork oscillators were used when one needed accurate frequency in the audio range. That's because dividing down high frequency quartz oscillators to, say, 60 Hz or 400 Hz required lots of circuitry. Not sure if Neal's reference to vibrating reed is what we would call a tuning fork, or if it's something else. Here in the US General Radio made precision tuning fork oscillators. Model numbers 213, 723, 813, 815. One example is at http://leapsecond.com/museum/gr815b/ Also check out old issues of General Radio Experimenter magazine for details on these wonderful instruments. Pendulum clocks were also used in power plants around the world to keep the grid synchronized. There is occasional discussion about this on clock collecting or horology forums. They are precious and can be extremely accurate, as good as a second a year. Since pendulum clocks were better long-term timekeepers and generated only 0.5 or 1 Hz signals, a PDTF (Pendulum Disciplined Tuning Fork) made sense. Has a nice ring to it, doesn't it. /tvb - Original Message - From: Andy Bardagjy a...@bardagjy.com To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Friday, January 09, 2015 9:22 AM Subject: [time-nuts] Mechanical 1PPS Oscillator Disciplining From a fascinating (albeit long) article about transatlantic communication cables http://archive.wired.com/wired/archive/4.12/ffglass.html On the bottom of page 45 to the top of page 46 Each piece of equipment on this tabletop is built around a motor that turns over at the same precise frequency. None of it would work - no device could communicate with any other device - unless all of those motors were spinning in lockstep with one another. The transmitter, regenerator/retransmitter, and printer all had to be in sync even though they were thousands of miles apart. This feat is achieved by means of a collection of extremely precise analog machinery. The heart of the system is another polished box that contains a vibrating reed, electromagnetically driven, thrumming along at 30 cycles per second, generating the clock pulses that keep all the other machines turning over at the right pace. The reed is as precise as such a thing can be, but over time it is bound to drift and get out of sync with the other vibrating reeds in the other stations. In order to control this tendency, a pair of identical pendulum clocks hang next to each other on the wall above. These clocks feed steady, one-second timing pulses into the box housing the reed. The reed, in turn, is driving a motor that is geared so that it should turn over at one revolution per second, generating a pulse with each revolution. If the frequency of the reed's vibration begins to drift, the motor's speed will drift along with it, and the pulse will come a bit too early or a bit too late. But these pulses are being compared with the steady one-second pulses generated by the double pendulum clock, and any difference between them is detected by a feedback system that can slightly speed up or slow down the vibration of the reed in order to correct the error. The result is a clock so steady that once one of them is set up in, say, London, and another is set up in, say, Cape Town, the machinery in those two cities will remain synched with each other indefinitely. Does anyone know any other history about that particular piece of equipment? Cheers! Andy ◉ Bardagjy.com ◉ +1-404-964-1641 ___ 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] Mechanical 1PPS Oscillator Disciplining
From a fascinating (albeit long) article about transatlantic communication cables http://archive.wired.com/wired/archive/4.12/ffglass.html On the bottom of page 45 to the top of page 46 Each piece of equipment on this tabletop is built around a motor that turns over at the same precise frequency. None of it would work - no device could communicate with any other device - unless all of those motors were spinning in lockstep with one another. The transmitter, regenerator/retransmitter, and printer all had to be in sync even though they were thousands of miles apart. This feat is achieved by means of a collection of extremely precise analog machinery. The heart of the system is another polished box that contains a vibrating reed, electromagnetically driven, thrumming along at 30 cycles per second, generating the clock pulses that keep all the other machines turning over at the right pace. The reed is as precise as such a thing can be, but over time it is bound to drift and get out of sync with the other vibrating reeds in the other stations. In order to control this tendency, a pair of identical pendulum clocks hang next to each other on the wall above. These clocks feed steady, one-second timing pulses into the box housing the reed. The reed, in turn, is driving a motor that is geared so that it should turn over at one revolution per second, generating a pulse with each revolution. If the frequency of the reed's vibration begins to drift, the motor's speed will drift along with it, and the pulse will come a bit too early or a bit too late. But these pulses are being compared with the steady one-second pulses generated by the double pendulum clock, and any difference between them is detected by a feedback system that can slightly speed up or slow down the vibration of the reed in order to correct the error. The result is a clock so steady that once one of them is set up in, say, London, and another is set up in, say, Cape Town, the machinery in those two cities will remain synched with each other indefinitely. Does anyone know any other history about that particular piece of equipment? Cheers! Andy ◉ Bardagjy.com ◉ +1-404-964-1641 ___ 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.
