[time-nuts] Distributed DDS
Dear nuts, Triggered by Ulrich's very interesting thread on nasty DDS features, I would like to submit for comments an idea for an application of DDS technology which hopefully does not suffer from them. We have a need at CERN to distribute RF signals (those used for driving particle-accelerating cavities) over long distances (several km) in a phase-compensated way. We can already have a phase-compensated fixed 125 MHz clock everywhere thanks to the White Rabbit (WR) network (see http://www.ohwr.org/projects/white-rabbit/wiki). The nodes in the WR network will be made with FMC carrier boards in several formats, e.g. this PCIe card with on-board DDS and PLL chips: http://www.ohwr.org/projects/fmc-pci-carrier/wiki. The idea to transmit an arbitrary RF signal from one node to another is the following: - Feed the reference RF to one of the nodes (equipped with a suitable interfacing FMC) and have the DDS take the place of the usual VCO in a PLL configuration, i.e. have the DDS track the incoming RF signal by suitably modifying its control word in real time. Of course, the RF must be a relatively stable signal. In this configuration I expect to have the low frequency noise of the RF reference at the output of this PLL, not the artifacts described in the nasty DDS features thread. The DDS is clocked with the WR 125 MHz clock or a clock derived from it. All WR nodes have easy access to this clock. - Time-tag all correction words sent to the DDS in this PLL node with a good WR UTC tag. - Broadcast these correction words with their associated UTC tags to all interested nodes, with enough time in advance so that everybody gets them by some suitable UTC execution time. Typical delays through a WR network are in the 10-100 us area and upper-bounded so one can do worst-case design. - Have all receiving nodes replay these control words at the same UTC times everywhere. This Distributed DDS (D3S) scheme should result in good (as good as the UTC-distribution capabilities of WR) RF signal re-generation everywhere, with a constant delay with respect to the original signal which is not a problem for us. It also has the potential of sending more than one RF signal through the same link quite naturally. As this is a new application for us, I was wondering if some among you have been confronted with such problems in the past or have tried to do something similar to this D3S idea. Thanks! Javier ___ 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] Temperature stability for Thunderbolt: results
With the temperature stabilized, compared to just 1 degree swings in temperature I see a 10 times improvement in the 1PPS standard deviation, and a 3 times improvement in the oscillator and dac control voltage. - Between that data and LH's EFC plot you should have some pretty good information on just how much the temperature control is helping. ___ 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] spur prediction DDS software
Hi, Is there a DDS spur prediction software around ? I mean for an arbitrary DDS design, like I would implement with logic or fpga etc. A code where I can enter nr of bits adc bits etc. (not a thing for a particular analog-devices chip or other dds chip) tks. Luis Cupido ct1dmk. ___ 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] spur prediction DDS software
On 1/27/11 5:17 AM, Luis Cupido wrote: Hi, Is there a DDS spur prediction software around ? Not generically.. There is a dissertation out there with some matlab code. I'll see if I can find a link Most of the time what I do is write a little program in matlab/octave, run a bunch of samples, and FFT it. That way you can model things like error feedback or truncation effects. I mean for an arbitrary DDS design, like I would implement with logic or fpga etc. A code where I can enter nr of bits adc bits etc. (not a thing for a particular analog-devices chip or other dds chip) tks. Luis Cupido ct1dmk. ___ 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] Temperature stability for Thunderbolt: results
Hi There are a bunch of cheap little USB thermometers out there ($10 or so). [] Bob Thanks for that heads-up, Bob, I had missed those. I just ordered a couple, although it will now be after the Chinese New Year when they arrive! Cheers, 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] spur prediction DDS software
On 1/27/11 5:17 AM, Luis Cupido wrote: Hi, Is there a DDS spur prediction software around ? I mean for an arbitrary DDS design, like I would implement with logic or fpga etc. A code where I can enter nr of bits adc bits etc. (not a thing for a particular analog-devices chip or other dds chip) while hunting for the software I had used before, I ran across a newer paper by Toroysan and Wilson titled Exact analysis of DDS spurs and SNR due to phase truncation and arbitrary phase-to-amplitude errors , aug 2005 frequency control symposium. Toroysan has a patent on a system for designing DDSes too. Vankka's book/dissertation is online, as well. ___ 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] spur prediction DDS software
On 1/27/11 5:17 AM, Luis Cupido wrote: Hi, Is there a DDS spur prediction software around ? I mean for an arbitrary DDS design, like I would implement with logic or fpga etc. A code where I can enter nr of bits adc bits etc. here's a good start.. Martin Pechanec's work... http://geociti.es/CapeCanaveral/5611/dds.html His simulator is downloadable from the page, and it does a lot of what you want to do. (and, it mostly runs in Octave, too. I haven't fooled with it a few years, so I don't remember what didn't work) ___ 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] Update -- Comparing 10 MHz Oscillators at 10 GHz
Hi As a first order approximation for phase noise: Feed them both into a mixer and look at the output on a sound card after some amplification. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Lester Veenstra Sent: Thursday, January 27, 2011 2:05 AM To: rich...@karlquist.com; 'Discussion of precise time and frequency measurement' Subject: Re: [time-nuts] Update -- Comparing 10 MHz Oscillators at 10 GHz For close in phase noise, the kind that is usually of interest, and hardest to measure, it does work in general, with the PLL loop bandwidth limitation noted below for higher frequency noise. Lester B Veenstra MØYCM K1YCM les...@veenstras.com m0...@veenstras.com k1...@veenstras.com US Postal Address: PSC 45 Box 781 APO AE 09468 USA UK Postal Address: Dawn Cottage Norwood, Harrogate HG3 1SD, UK Telephones: Office: +44-(0)1423-846-385 Home: +44-(0)1943-880-963 Guam Cell: +1-671-788-5654 UK Cell: +44-(0)7716-298-224 US Cell: +1-240-425-7335 Jamaica: +1-876-352-7504 This e-mail and any documents attached hereto contain confidential or privileged information. The information is intended to be for use only by the individual or entity to whom they are addressed. If you are not the intended recipient or the person responsible for delivering the e-mail to the intended recipient, be aware that any disclosure, copying, distribution or use of the contents of this e-mail or any documents attached hereto is prohibited. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Rick Karlquist Sent: Thursday, January 27, 2011 3:38 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Update -- Comparing 10 MHz Oscillators at 10 GHz brucekar...@aol.com wrote: ...The bricks are extremely low noise in their own right and are locked with a narrow loop that prevents source noise from degrading them. Rick Karlquist N6RK ___ 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] power spectrum of hard limiter output
Hi If anybody is doing PLL's and does not have a copy of that book - go out and get it. In the second edition, limiters are in section 6.4 starting on page 125. The good stuff (complete with Bessel functions) is on pages 126 and 127. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of ehydra Sent: Wednesday, January 26, 2011 7:31 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] power spectrum of hard limiter output Hm Magnus - I heard of it as a standard text book but never looked inside. And not known that it describes limiter behaviour. Anyway. Now I have a version of 2004, 3rd edition, and cannot find the mentioned chapter. Please post a little more info, so I can find with keywords. Thank you! - Henry Magnus Danielson schrieb: On 26/01/11 00:35, ehydra wrote: Hi Magnus - What book? This one maybe: Gardner F M PHASELOCK TECHNIQUES Wiley Sons 1966 Yes, but there is later revisions of it. A classic on PLLs. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] spur prediction DDS software
Hi There's some stuff in Matlab if you have the right package add-on's. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Luis Cupido Sent: Thursday, January 27, 2011 8:18 AM To: Discussion of precise time and frequency measurement Subject: [time-nuts] spur prediction DDS software Hi, Is there a DDS spur prediction software around ? I mean for an arbitrary DDS design, like I would implement with logic or fpga etc. A code where I can enter nr of bits adc bits etc. (not a thing for a particular analog-devices chip or other dds chip) tks. Luis Cupido ct1dmk. ___ 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] power spectrum of hard limiter output
Even the original is a good classic on PLLs. I have an original photocopy of the typed pre-publication volume, as well as the actual book. Regarding hard limiters, we did a lot of study on their behavior on the resulting power spectra. We use a one bit quantizer of ASW signals and then displayed the output power spectra on graph paper, back in the late 60's early 70's. I have some of the original papers on the effects of hard limiting of signals, with AWGN, however, they are downstairs in the inner sanctum and to find them would be a challenge. Maybe if I get ambitious I'll venture downstairs and see if I can locate the folders. Would be glad to scan them. Regards - Mike Mike B. Feher, EOZ Inc. 89 Arnold Blvd. Howell, NJ, 07731 732-886-5960 office 908-902-3831 cell -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Magnus Danielson Sent: Wednesday, January 26, 2011 12:34 AM To: time-nuts@febo.com Subject: Re: [time-nuts] power spectrum of hard limiter output On 26/01/11 00:35, ehydra wrote: Hi Magnus - What book? This one maybe: Gardner F M PHASELOCK TECHNIQUES Wiley Sons 1966 Yes, but there is later revisions of it. A classic on PLLs. Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Temperature stability for Thunderbolt: results
Hi With a normal TBolt running on the bench, it's very obvious that temperature and EFC are directly related to each other. With a little scaling (and possibly an inversion) the plot of one lays down on top of the other. As long as you can eyeball that kind of relation, there's an issue. Why watch EFC? My assumption is that the OCXO has been on for a good long while and that it's settled down. In a Time Nut environment that's likely a good assumption. I'm also assuming that the supply voltages are stable as is the internal DAC. One is a pretty good bet for list members, the other is a complete guess. Final assumption is that the short term on the OCXO is significantly better than GPS over modest time ranges (very likely true). If all that's true, what you are watching on the EFC is the TBolt correct out the OCXO TC. You could go crazy with auto correlation stuff, but I'm not sure your measure of the outside temperature is going to be good enough to make more than an eyeball approach useful. By this (quite possibly imperfect) measure: When the EFC goes down 3:1, you have improved the thermals by 3X. If you started at 1 C swings, the OCXO is now seeing 1/3 C swings. Ultimately what you would like is a setup that never needs to change the EFC (much), so you could run a nice long loop and still have the PPS stay lined up. That *should* give you a significant improvement in short term out of the TBolt. Since it's done with the EFC plot and verified with a cheap thermometer (rather than a bunch of crazy to find gear) it's a reasonable basement Time Nut thing to do. Certainly should add that without all the work done on Lady Heather, you wouldn't have a chance of doing any of this. Can't eyeball a plot you don't have... Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Mark Sims Sent: Thursday, January 27, 2011 7:05 AM To: time-nuts@febo.com Subject: [time-nuts] Temperature stability for Thunderbolt: results With the temperature stabilized, compared to just 1 degree swings in temperature I see a 10 times improvement in the 1PPS standard deviation, and a 3 times improvement in the oscillator and dac control voltage. - Between that data and LH's EFC plot you should have some pretty good information on just how much the temperature control is helping. ___ 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] power spectrum of hard limiter output
Hi, On 27/01/11 01:30, ehydra wrote: Hm Magnus - I heard of it as a standard text book but never looked inside. And not known that it describes limiter behaviour. Anyway. Now I have a version of 2004, 3rd edition, and cannot find the mentioned chapter. Please post a little more info, so I can find with keywords. Mine is second edition. It is part of Chapter six - Loop components and there is in mine a sub-chapter 6.4 Limiters which gives these descriptions prior to discuss noise effects on phase-detectors. 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] power spectrum of hard limiter output
Hi Mike, On 27/01/11 18:25, Mike Feher wrote: Even the original is a good classic on PLLs. I have an original photocopy of the typed pre-publication volume, as well as the actual book. Regarding hard limiters, we did a lot of study on their behavior on the resulting power spectra. We use a one bit quantizer of ASW signals and then displayed the output power spectra on graph paper, back in the late 60's early 70's. I have some of the original papers on the effects of hard limiting of signals, with AWGN, however, they are downstairs in the inner sanctum and to find them would be a challenge. Maybe if I get ambitious I'll venture downstairs and see if I can locate the folders. Would be glad to scan them. Please do. I enjoy reading old papers. Helps to get things in perspective. :) 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] Temperature stability for Thunderbolt: results
Bob wrote: If all that's true, what you are watching on the EFC is the TBolt correct out the OCXO TC. Agreed (well, superimposed upon its correction of all other drift mechanisms). By this (quite possibly imperfect) measure: When the EFC goes down 3:1, you have improved the thermals by 3X. If you started at 1 C swings, the OCXO is now seeing 1/3 C swings. Agreed (re: the EFC component that correlates to changes in Tbolt ambient temperature). Ultimately what you would like is a setup that never needs to change the EFC (much), so you could run a nice long loop and still have the PPS stay lined up. That *should* give you a significant improvement in short term out of the TBolt. Alternatively, if you lengthen the thermal time constant from ambient to Tbolt so that it is substantially longer than the time constant of the loop chosen for best drift performance, AND the Tbolt control loop has sufficient gain, the Tbolt control loop will take care of both. There is a limit to how long you want the Tbolt TC to be -- generally something in the neighborhood of 1000 seconds -50/+100% -- based on the tau at which the particular XO in your Tbolt transitions to its random-walk behavior. Accordingly, you have a good idea what sort of TC you need from ambient to Tbolt so that it is substantially longer. I set mine up that way (as described in a previous post) before LH had the temperature control feature, and it appears that the Tbolt control loop has plenty of gain to suppress drift from the sort of ambient temperature fluctuations one finds in a home shop environment below the random fluctuations from the on-board XO. In this connection, note that the oven will allow the crystal to vary in temperature by a certain amount even if the ambient temperature outside the oven is perfectly constant, and we have no control over that loop. Also note that there will be temperature gradients within the Tbolt between its internal temperature sensor and the outside of the oven, and that these will vary over time. Thus, beyond a certain point, holding the temperature at the Tbolt's internal temperature sensor constant will not further improve the temperature regulation of the crystal itself. When this is done, the EFC will still show a component that tracks the ambient temperature reported by the internal temperature sensor -- but this will be an extremely slow variation, and indicates that the control loop is successfully handling ambient temperature changes. My point is not that one shouldn't try to hold the Tbolt ambient temperature (as reported by its internal temperature sensor) constant, just that it may not be a greater benefit in practice than simply slowing the ambient-to-Tbolt time constant enough to let the Tbolt's control loop handle variations in ambient temperature -- at least for the modest swings likely to be encountered in a home shop environment. Ideally, one would like accurate temperature information from the crystal itself, and would use external controls to hold the crystal temperature constant directly. This could be tricky if the existing oven loop were left intact, fully enclosed within our external loop -- likely, one would need to redesign the entire loop structure. Certainly should add that without all the work done on Lady Heather, you wouldn't have a chance of doing any of this. Can't eyeball a plot you don't have... Amen to that. Best regards, Charles ___ 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] power spectrum of hard limiter output
I found chapter Appendix 7A Analysis of interference in a hard limiter There is a half page with a couple of formulas. Not much, not practically oriented. Only idealized hard-limiters. I'm interested in SOFT-limiters! Hm. Does the writer seen a real working system once upon in time? - Henry Magnus Danielson schrieb: Hi, On 27/01/11 01:30, ehydra wrote: Hm Magnus - I heard of it as a standard text book but never looked inside. And not known that it describes limiter behaviour. Anyway. Now I have a version of 2004, 3rd edition, and cannot find the mentioned chapter. Please post a little more info, so I can find with keywords. Mine is second edition. It is part of Chapter six - Loop components and there is in mine a sub-chapter 6.4 Limiters which gives these descriptions prior to discuss noise effects on phase-detectors. 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] spur prediction DDS software
The best once I found is this: http://www.holmea.demon.co.uk/FracN/Simulate.htm - Henry Luis Cupido schrieb: Hi, Is there a DDS spur prediction software around ? I mean for an arbitrary DDS design, like I would implement with logic or fpga etc. A code where I can enter nr of bits adc bits etc. (not a thing for a particular analog-devices chip or other dds chip) ___ 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] SYSTRON-DONNER 3522 -IEEE 448 BUSSER II
I've just listed this item on EBay: 32064101. Low starting bid of GBP0.99 A real blast from the past, but may be of interest to someone in the group. Will be digging out some other stuff shortly as part of a move/downsize. Cheers Rob K ___ 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] Tbolt Temp Specs
List, The temperature numbers that members have published are very impressive. My question is: What does the tbolt use for a temperature sensor and is there or has anyone been able to independently verify that the stated numbers are accurate? Of course if they are working extremely well it may be a moot point. Regards, Perrier ___ 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] Mass vs BTU Function
List, Please help me with this physics question. If one has a given cube, say 2 x 2 x 2 inches. And one has the choice of aluminum, copper, or lead (just for an example). Will each store or hold the same amount of BTUs or does the density make a difference? IF the density makes a difference, can someone give me the approximate difference? The practical end of this question is consideration of thermal mass surrounding an oscillator, TIA Perrier ___ 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] Temperature stability for Thunderbolt: results
With the temperature stabilized, compared to just 1 degree swings in temperature I see a 10 times improvement in the 1PPS standard deviation, and a 3 times improvement in the oscillator and dac control voltage. Mark, Do you have any measurements of the actual 1PPS output with and without temperature stabilization? The LH numbers being quoted recently are internal loop measurements rather than real 10 MHz or 1PPS BNC outputs of the TBolt, yes? /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] Mass vs BTU Function
The heat capacity of an object is the Heat Capacity = M * Cp M = Mass Cp = Specific Heat (at constant pressure) M = Vol * SG SG = Specific Gravity ( = density/density of water) So, Heat Capacity = Vol * SG * Cp If you want to know how much heat is required to change tempo: Heat = Vol * SG * Cp * (delta T) - all in same unit system of course. -John === List, Please help me with this physics question. If one has a given cube, say 2 x 2 x 2 inches. And one has the choice of aluminum, copper, or lead (just for an example). Will each store or hold the same amount of BTUs or does the density make a difference? IF the density makes a difference, can someone give me the approximate difference? The practical end of this question is consideration of thermal mass surrounding an oscillator, TIA Perrier ___ 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] Mass vs BTU Function
Thermal energy in metals are measured in 'pro kg'. The rest is just calculation. From a practical standpoint I would use copper. You can solder and weld it more easely. Look for how head-fin spreaders work for CPUs. - Henry Perry Sandeen schrieb: List, Please help me with this physics question. If one has a given cube, say 2 x 2 x 2 inches. And one has the choice of aluminum, copper, or lead (just for an example). Will each store or hold the same amount of BTUs or does the density make a difference? IF the density makes a difference, can someone give me the approximate difference? The practical end of this question is consideration of thermal mass surrounding an oscillator, TIA Perrier ___ 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] Clock Calibration
List, I was reading some of the history of mechanical clocks and was astonished to see that one guaranteed its accuracy to 2 milliseconds per day! (And it was) Now this same clock when tested with modern equipment tested to be accurate to 200 micro-seconds per day. Astonishing! This got to wondering how the heck they were able to calibrate a clock to milliseconds per day back then? And as extension to that question, how do they prove the accuracy of F1 or other similar time standards? Regards, Perrier ___ 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] Clock Calibration
Hi Perrier: When was this? Do you have a URL? Have Fun, Brooke Clarke http://www.PRC68.com Perry Sandeen wrote: List, I was reading some of the history of mechanical clocks and was astonished to see that one guaranteed its accuracy to 2 milliseconds per day! (And it was) Now this same clock when tested with modern equipment tested to be accurate to 200 micro-seconds per day. Astonishing! This got to wondering how the heck they were able to calibrate a clock to milliseconds per day back then? And as extension to that question, how do they prove the accuracy of F1 or other similar time standards? Regards, Perrier ___ 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] Tbolt Temp Specs
Perrier- My question is: What does the tbolt use for a temperature sensor... The Thunderbolt uses the DS1620 http://pdfserv.maxim-ic.com/en/ds/DS1620.pdf -Arthur ___ 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] SYSTRON-DONNER 3522 -IEEE 448 BUSSER II
Hi Rob, don't the worst typos always end up in the title! cheers, ian Date: Thu, 27 Jan 2011 20:08:10 - From: Rob Kimberley r...@timing-consultants.com Subject: [time-nuts] SYSTRON-DONNER 3522 -IEEE 448 BUSSER II To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Message-ID: 000301cbbe5d$ebff1570$c3fd4050$@timing-consultants.com Content-Type: text/plain; charset=us-ascii I've just listed this item on EBay: 32064101. Low starting bid of GBP0.99 A real blast from the past, but may be of interest to someone in the group. Will be digging out some other stuff shortly as part of a move/downsize. Cheers Rob K ___ 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] Clock Calibration
Boy I sure don't know but. I could make some assumptions especially if it were 100 years ago. I might guess its either a sun or star track and the fact that exactly 24 hours later it crossed. Granted the clock could be adjusted so that its tick would exactly cross. Most likely a light/candle and a small mirror on the pendulum This would not account for any of the effects we consider today. Just my crazy useless way of thinking. Regards Paul On Thu, Jan 27, 2011 at 3:55 PM, Perry Sandeen sandee...@yahoo.com wrote: List, I was reading some of the history of mechanical clocks and was astonished to see that one guaranteed its accuracy to 2 milliseconds per day! (And it was) Now this same clock when tested with modern equipment tested to be accurate to 200 micro-seconds per day. Astonishing! This got to wondering how the heck they were able to calibrate a clock to milliseconds per day back then? And as extension to that question, how do they prove the accuracy of F1 or other similar time standards? Regards, Perrier ___ 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] Temperature stability for Thunderbolt: results
At one time I took some data on a 5370A with a FTS4060 cesium as the reference. Those numbers tracked the self-reported numbers. I can't find the raw data anymore. Warren also pointed out that with the temperature stabilized you can increase the filter time constant 2-3 times over what a non-stabilized unit can run at. This makes an even bigger improvement in performance. I usually keep my filter set at 500 seconds. I need to see what 1000+ seconds will do. The Tbolt uses a DS1620 temp sensor in its high-resolution readout mode that gives around 0.01C raw resolution. The Tbolt filters this and spits out micro-degree resolution numbers. The absolute temperature accuracy is under 1 degree F, but for thermal management we are really only interested in resolution, not absolute values. I did check the consistency of the thermal environment in my box with a micro-degree resolution sensor and it was quite good. The difference in stability between where the D1620 sensor is and the oscillator was negligible. Do you have any measurements of the actual 1PPS output with and without temperature stabilization? The LH numbers being quoted recently are internal loop measurements rather than real 10 MHz or 1PPS BNC outputs of the TBolt, yes? ___ 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] Temperature stability for Thunderbolt: results
By this (quite possibly imperfect) measure: When the EFC goes down 3:1, you have improved the thermals by 3X. If you started at 1 C swings, the OCXO is now seeing 1/3 C swings. Agreed (re: the EFC component that correlates to changes in Tbolt ambient temperature). A number of posts have mentioned LH measurements and variations in DAC voltage or TI or OSC values. I'm curious how close to the truth this is. An analogy: suppose my goal is to drive 55 mph for a day as smoothly as possible. There are two judges. One judge is a passenger who at all times is looking at my foot. Over the hours they see me push the accelerator at varying depths; sometimes slacking off quite a bit and other times pushing fairly hard. Occasionally they even see me tap the brake. They collect all this raw data and make graphs and conclude that I am a mediocre driver since there was a lot of variation in my performance and I could have done much better. The other judge is a fully instrumented time nut in a vehicle behind me; watching the position, velocity, and acceleration of my car at all times to many decimal places. Moreover they collect environmental and road condition data. They see me keep really close to 55 mph regardless of the straight roads, or all those up and down hills; around gradual and tight curves, in daylight and at night, during the warmer day and cooler night. They imagine I must be highly motivated and alert, constantly and tirelessly adjusting acceleration to meet the demands of the uneven road and driving conditions. They conclude I'm an excellent driver. Which judge is more correct? Which judge is LH? If someone already has raw TBolt data (both internal and external, simultaneously) with and without fine temperature regulation let me know; we can see how well the judges compare. /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] SYSTRON-DONNER 3522 -IEEE 448 BUSSER II
Well spotted that man!! -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of gonzo . Sent: 27 January 2011 9:02 PM To: time-nuts Subject: Re: [time-nuts] SYSTRON-DONNER 3522 -IEEE 448 BUSSER II Hi Rob, don't the worst typos always end up in the title! cheers, ian Date: Thu, 27 Jan 2011 20:08:10 - From: Rob Kimberley r...@timing-consultants.com Subject: [time-nuts] SYSTRON-DONNER 3522 -IEEE 448 BUSSER II To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Message-ID: 000301cbbe5d$ebff1570$c3fd4050$@timing-consultants.com Content-Type: text/plain; charset=us-ascii I've just listed this item on EBay: 32064101. Low starting bid of GBP0.99 A real blast from the past, but may be of interest to someone in the group. Will be digging out some other stuff shortly as part of a move/downsize. Cheers Rob K ___ 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] Clock Calibration
Hi If you go by Wikipedia, 10 ms per day was considered pretty good in 1909. Shortt clocks came along in 1929 and are mentioned as 1 second per year. I suspect the 2 ms / day and 1 sec per year numbers are both referring to a Shortt. Simple answer is that all of this came along after you had electronics to compare stuff with. Calibration times were in months. Deviations between clocks in an ensemble were used to estimate shorter time periods. I don't find it to unbelievable that you could time an astronomical event to ~ 0.1 seconds or better without anything very fancy being involved. If you wanted to automate it, light sensors date back into the 1850's. Either way you could get data in less than a year that would confirm / deny your accuracy. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of paul swed Sent: Thursday, January 27, 2011 4:13 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Clock Calibration Boy I sure don't know but. I could make some assumptions especially if it were 100 years ago. I might guess its either a sun or star track and the fact that exactly 24 hours later it crossed. Granted the clock could be adjusted so that its tick would exactly cross. Most likely a light/candle and a small mirror on the pendulum This would not account for any of the effects we consider today. Just my crazy useless way of thinking. Regards Paul On Thu, Jan 27, 2011 at 3:55 PM, Perry Sandeen sandee...@yahoo.com wrote: List, I was reading some of the history of mechanical clocks and was astonished to see that one guaranteed its accuracy to 2 milliseconds per day! (And it was) Now this same clock when tested with modern equipment tested to be accurate to 200 micro-seconds per day. Astonishing! This got to wondering how the heck they were able to calibrate a clock to milliseconds per day back then? And as extension to that question, how do they prove the accuracy of F1 or other similar time standards? Regards, Perrier ___ 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] Temperature stability for Thunderbolt: results
Hi The assumption is that other than OCXO short term and aging - all the bumps and dips in the road have been eliminated. As I mentioned earlier that is indeed an assumption that has a lot of sub assumptions that go into it. It also assumes that GPS is correct over the time period involved. To put some numbers on all this, here's some guesses. Accuracies of GPS on the TBolt are an eyeball 2 ns or so. A thousand seconds is pretty long for an OCXO short term floor. That would give you 2x10^-9 / 1000 = 2x10^-12 as a limit on what's being done. At 10,000 seconds the OCXO would have to be 2x10^-13 - that's not happening. At 100 seconds it would need to be 2x10^-11 which is pretty high probability. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Tom Van Baak Sent: Thursday, January 27, 2011 4:37 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Temperature stability for Thunderbolt: results By this (quite possibly imperfect) measure: When the EFC goes down 3:1, you have improved the thermals by 3X. If you started at 1 C swings, the OCXO is now seeing 1/3 C swings. Agreed (re: the EFC component that correlates to changes in Tbolt ambient temperature). A number of posts have mentioned LH measurements and variations in DAC voltage or TI or OSC values. I'm curious how close to the truth this is. An analogy: suppose my goal is to drive 55 mph for a day as smoothly as possible. There are two judges. One judge is a passenger who at all times is looking at my foot. Over the hours they see me push the accelerator at varying depths; sometimes slacking off quite a bit and other times pushing fairly hard. Occasionally they even see me tap the brake. They collect all this raw data and make graphs and conclude that I am a mediocre driver since there was a lot of variation in my performance and I could have done much better. The other judge is a fully instrumented time nut in a vehicle behind me; watching the position, velocity, and acceleration of my car at all times to many decimal places. Moreover they collect environmental and road condition data. They see me keep really close to 55 mph regardless of the straight roads, or all those up and down hills; around gradual and tight curves, in daylight and at night, during the warmer day and cooler night. They imagine I must be highly motivated and alert, constantly and tirelessly adjusting acceleration to meet the demands of the uneven road and driving conditions. They conclude I'm an excellent driver. Which judge is more correct? Which judge is LH? If someone already has raw TBolt data (both internal and external, simultaneously) with and without fine temperature regulation let me know; we can see how well the judges compare. /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] Tbolt Temp Specs
The temperature numbers that members have published are very impressive. My question is: What does the tbolt use for a temperature sensor and is there or has anyone been able to independently verify that the stated numbers are accurate? Of course if they are working extremely well it may be a moot point. Perrier, The TBolt uses a DS1620 in a two step high-res mode. In this case the actual resolution varies from chip to chip and maybe even across temperature range but in the units I've tested seems to be under 1/100th of a degree, typically about 7 mK. I can give you more details if you wish. Note that this is resolution and not accuracy. But the good news is that for a closed system like this accuracy is not important; just resolution. As for the milli- and micro-kelvin numbers; well, that is a little misleading. Given a series of measurements you can always calculate an average and standard deviation. In a closed loop like a GPSDO or a temperature controlled box the average error will always decrease simply because one computes an average by dividing by N. But the readings are bounded by virtue of the closed loop. You'll find the stdev reaches a nominal value after a bunch of samples and remains pretty constant from then on. The mean error, on the other hand, has N as a divisor -- so the larger N gets the smaller the mean error number becomes. It turns out it doesn't mean anything. A more appropriate statistic is simply to quote the rms error value and leave it at that. Otherwise you get into a game where one person says their TBolt is stable to 30 mK per hour. The next person waits a week and says theirs is much better since it averages down to 0.1 mK. Not to be outdone, someone else waits a month and claims one micro-Kelvin stability. Hey, check out this tombstone: here lies the body of a time nut who kept his TBolt stable to ten pico-Kelvin over his lifetime. Quoting temperature regulation with an average over time is misleading. Just use an rms value. /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] Mass vs BTU Function
At 04:18 PM 1/27/2011, J. Forster wrote... If you are considering conductivity for dynamic reasons, the correct figure of merit is Thermal Diffusivity = (Specific Heat) / (Thermal Conductivity) If you want a thermal mass to help control temperature swings, the more heat capacity is good. Isn't more thermal conductivity also desired? It seems like a substance with low conductivity wouldn't gather/release heat well. If more of both is desired, shouldn't the figure of merit should then be (specific heat * thermal conductivity), since you want more of both? In answer to the original question, which asked for heat capacity per volume. One need only multiply the specific heat by the density. For the examples given, plus iron and water: (substance) (specific heat) (density) (heat capacity?) ( ) (kJ/kg K) (g/ml^3)(kJ/l K) Al 0.91 2.7 2.5 Cu 0.39 9.96 3.9 Pb 0.13 11.36 1.5 Fe 0.46 7.87 3.6 H2O 4.2 1.0 4.2 So, copper is best, but iron (steel shouldn't be much different) is pretty close and very much cheaper. Water is better and cheaper still, but can be a bit messy. ___ 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] Mass vs BTU Function
If you want the thermal mass to behave close to an isothermal body, diffusivity is very important. For example, a large mass of still water has high heat capacity, but poor diffusivity. Much of the heat capacity is useless. -John == At 04:18 PM 1/27/2011, J. Forster wrote... If you are considering conductivity for dynamic reasons, the correct figure of merit is Thermal Diffusivity = (Specific Heat) / (Thermal Conductivity) If you want a thermal mass to help control temperature swings, the more heat capacity is good. Isn't more thermal conductivity also desired? It seems like a substance with low conductivity wouldn't gather/release heat well. If more of both is desired, shouldn't the figure of merit should then be (specific heat * thermal conductivity), since you want more of both? In answer to the original question, which asked for heat capacity per volume. One need only multiply the specific heat by the density. For the examples given, plus iron and water: (substance) (specific heat) (density) (heat capacity?) ( ) (kJ/kg K) (g/ml^3)(kJ/l K) Al 0.91 2.7 2.5 Cu 0.39 9.96 3.9 Pb 0.13 11.36 1.5 Fe 0.46 7.87 3.6 H2O 4.2 1.0 4.2 So, copper is best, but iron (steel shouldn't be much different) is pretty close and very much cheaper. Water is better and cheaper still, but can be a bit messy. ___ 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] Mass vs BTU Function
On Thu, Jan 27, 2011 at 12:38 PM, Perry Sandeen sandee...@yahoo.com wrote: List, Please help me with this physics question. If one has a given cube, say 2 x 2 x 2 inches. And one has the choice of aluminum, copper, or lead (just for an example). Will each store or hold the same amount of BTUs or does the density make a difference? I think it's specif heat * mass. So it you are limited by the size of a 2 cube then even if one material has worse specific, if it had more density then more mass would fit in the same 2 cube.If you were weight limited then only specific heat matters. But in your case I think, from memory silver is good then copper I think you get different answers if the project is volume limited then if it is weight limited or cost limited. Certainly cost would have you with copper over silver If you just ask what's best? with no limits on volume, weight or cost I bet you end up using an exotic liquid. I worked on a project once where we just used a water tank. -- = Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Mass vs BTU Function
jim...@earthlink.net said: Most metals have a specific heat around .34, where water is 1.0. ( so .34 BTU to raise a pound od aluminum by 1 deg F) Where did you get that? This table says: Aluminum 0.215 Copper 0.092 Iron0.107 Lead0.031 http://phoenix.phys.clemson.edu/labs/223/spheat/index.html (units are cal/g/C) Google found similar numbers in several other tables. Perhaps I'm being too picky on what you mean by around, but a factor of 7 seems big enough to be interesting. -- 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] Mass vs BTU Function
At 05:33 PM 1/27/2011, J. Forster wrote... If you want the thermal mass to behave close to an isothermal body, diffusivity is very important. For example, a large mass of still water has high heat capacity, but poor diffusivity. Much of the heat capacity is useless. If the equation given [Thermal Diffusivity = (Specific Heat) / (Thermal Conductivity)] is correct, then lower conductivity is desired for greater diffusitivity. I'm not clear on how low conductivity helps make an isothermal mass - intuitively, it seems the opposite is desired, so that any local temperature variations are quickly balanced through conduction. ___ 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] Mass vs BTU Function
I got the Thermal Diffusivity definition upside down. -John = At 05:33 PM 1/27/2011, J. Forster wrote... If you want the thermal mass to behave close to an isothermal body, diffusivity is very important. For example, a large mass of still water has high heat capacity, but poor diffusivity. Much of the heat capacity is useless. If the equation given [Thermal Diffusivity = (Specific Heat) / (Thermal Conductivity)] is correct, then lower conductivity is desired for greater diffusitivity. I'm not clear on how low conductivity helps make an isothermal mass - intuitively, it seems the opposite is desired, so that any local temperature variations are quickly balanced through conduction. ___ 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] Clock Calibration
Hi This is an interesting concept of measuring or comparing without electronics. Dont forget the scientists of former eras has some quite inovative bits of kit. the CRT dated from the 1920 but Victorians used a sooted glass slide carried on a small trolley that was moved by a falling weight.a storage 'scope forsooth :-)) I believe you will find Bell used a similar item in his speech investigations. Also, yes time was cheaper then so a test period of days would be acceptable..it only very recenly we have become so impatient :-)) It would probably be relatively easy to divide the swing of a long pendulum up in to 10ths or even 20th of a second and your reference would be a transit telescope, or, I believe, the Moon and a church steeple ?? was that Harrisons early work with the all wooden mechanisms? Alan G3NYK - Original Message - From: Bob Camp li...@rtty.us To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Sent: Thursday, January 27, 2011 9:56 PM Subject: Re: [time-nuts] Clock Calibration Hi If you go by Wikipedia, 10 ms per day was considered pretty good in 1909. Shortt clocks came along in 1929 and are mentioned as 1 second per year. I suspect the 2 ms / day and 1 sec per year numbers are both referring to a Shortt. Simple answer is that all of this came along after you had electronics to compare stuff with. Calibration times were in months. Deviations between clocks in an ensemble were used to estimate shorter time periods. I don't find it to unbelievable that you could time an astronomical event to ~ 0.1 seconds or better without anything very fancy being involved. If you wanted to automate it, light sensors date back into the 1850's. Either way you could get data in less than a year that would confirm / deny your accuracy. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of paul swed Sent: Thursday, January 27, 2011 4:13 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Clock Calibration Boy I sure don't know but. I could make some assumptions especially if it were 100 years ago. I might guess its either a sun or star track and the fact that exactly 24 hours later it crossed. Granted the clock could be adjusted so that its tick would exactly cross. Most likely a light/candle and a small mirror on the pendulum This would not account for any of the effects we consider today. Just my crazy useless way of thinking. Regards Paul On Thu, Jan 27, 2011 at 3:55 PM, Perry Sandeen sandee...@yahoo.com wrote: List, I was reading some of the history of mechanical clocks and was astonished to see that one guaranteed its accuracy to 2 milliseconds per day! (And it was) Now this same clock when tested with modern equipment tested to be accurate to 200 micro-seconds per day. Astonishing! This got to wondering how the heck they were able to calibrate a clock to milliseconds per day back then? And as extension to that question, how do they prove the accuracy of F1 or other similar time standards? Regards, Perrier ___ 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] Clock Calibration
On Thu, Jan 27, 2011 at 12:55 PM, Perry Sandeen sandee...@yahoo.com wrote: ...how the heck they were able to calibrate a clock to milliseconds per day back then? Let it run for 1,000 days, then you only need to be able to measure to the nearest second to get to ms per day. Or maybe you can measure to 0.1 seconds so it only takes 100 days. The trouble is that using this method you don't know the average error. A good example is an eccentric gear that makes a second hand run fast then slow but if averaged over a long period is near perfect. I doubt they were able to catch stuff like that. -- = Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
[time-nuts] worth salvaging ?
I'm getting ready to scrap a bunch of the Odetics GPStar's I have for the cool 5x7 HP LED displays Of the 11 antenna/down converters I've found one works. http://petelancashire.com/gallery/main.php?g2_itemId=19820 I'd like the lists opinion if saving the OCXO is worth puling of the board http://www.microcrystal.com/CMSPages/GetFile.aspx?nodeguid=6f5af9ba-b6a1-4bae-bab7-5e4e95a5c796 The one on the GPStar is the OCXO-BV5 -pete ___ 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] spur prediction DDS software
Luis Cupido wrote: Is there a DDS spur prediction software around ? I mean for an arbitrary DDS design, like I would implement with logic or fpga etc. That dds_oddities.pdf file I linked to yesterday has a couple references on page 4: - Martin Pechanec’s MATLAB scripts ( mentioned earlier by Jim L. ), - Zs. Pápay’s website and Mathcad files: http://www.hit.bme.hu/people/papay/sci/DDS/simul.htm I'd second Jim's suggestion of trying the Matlab scripts in Octave, I'd guess that the numerical sections would port easily but the GUI stuff might need some rework. There's also a Mathcad-like free program called SMath Studio ( which I haven't actually used yet ) that might prove useful to try setting up a model similar to those done in Mathcad. Note that the close-in phase truncation stuff discussed earlier has a very long repetition period, so for big phase accumulators you need either a huge FFT time record to see the phase truncation rollovers, or else use a shorter FFT record and preset the phase accumulator to a value shortly before the rollover. Brian ___ 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] worth salvaging ?
On Thu, Jan 27, 2011 at 3:54 PM, Pete Lancashire p...@petelancashire.com wrote: I'd like the lists opinion if saving the OCXO is worth puling of the board You mean is the OCXO worth your time to salvage it? I don't know but from those photos I see 100 parts that are worth my time to salvage. I look at those photos and see a goldmine of parts. I'd even salvage the little bead inductors and dip swiches The trick is not to worry at all about collateral damage on gear that is headed to the dumpster. If you think that way then salvage takes very little time. -- = Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Temperature stability for Thunderbolt: results
On 27/01/11 22:37, Tom Van Baak wrote: By this (quite possibly imperfect) measure: When the EFC goes down 3:1, you have improved the thermals by 3X. If you started at 1 C swings, the OCXO is now seeing 1/3 C swings. Agreed (re: the EFC component that correlates to changes in Tbolt ambient temperature). A number of posts have mentioned LH measurements and variations in DAC voltage or TI or OSC values. I'm curious how close to the truth this is. There are three observables to use: time measurements (GPS t measurement) frequency measurements (GPS f measurement) DAC control values (PLL PI-loop output) The last one is scaled by the EFC sensitivity which is uncalibrated and non-linear. The time and frequency measures is the observables towards GPS, for the car analogy precision measurements against reference points along the road. 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] power spectrum of hard limiter output
On 1/27/11 11:19 AM, ehydra wrote: I found chapter Appendix 7A Analysis of interference in a hard limiter There is a half page with a couple of formulas. Not much, not practically oriented. Only idealized hard-limiters. I'm interested in SOFT-limiters! Soft limiters are even more complex to analyze. Most of the hardlimiter in noise papers point out that when the signal/noise ratio is in the right range, it acts like a soft limiter with a gaussian characteristic. ___ 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] Mass vs BTU Function
On 1/27/11 3:20 PM, Hal Murray wrote: jim...@earthlink.net said: Most metals have a specific heat around .34, where water is 1.0. ( so .34 BTU to raise a pound od aluminum by 1 deg F) Where did you get that? probably misremembering.. Standing in an airport terminal trying to figure out whether to wait for my perpetually delayed flight, or give up and find a hotel... Forgive me... There's something for heat capacity that is 0.34, though.. maybe gases? I did do some googling and found this interesting statement in Wikipedia Another way of stating this, is that the volume-specific heat capacity (volumetric heat capacity) of solid elements is roughly a constant. The molar volume of solid elements is very roughly constant, and (even more reliably) so also is the molar heat capacity for most solid substances. These two factors determine the volumetric heat capacity, which as a bulk property may be striking in consistency.For example, the element uranium is a metal which has a density almost 36 times that of the metal lithium, but uranium's specific heat capacity on a volumetric basis (i.e. per given volume of metal) is only 18% larger than lithium's. This table says: Aluminum 0.215 Copper 0.092 Iron0.107 Lead0.031 http://phoenix.phys.clemson.edu/labs/223/spheat/index.html (units are cal/g/C) Google found similar numbers in several other tables. Perhaps I'm being too picky on what you mean by around, but a factor of 7 seems big enough to be interesting. ___ 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] TBolt et al
Hi all, I'm building a frequency master unit based on the Tbolt with associated buffers and dividers to give multiple frequencies and outputs plus utilising the PPS to provide the ref for an embedded linux box to provide NTP. This will provide the 10Mhz and others as the master lock for my lab. So. with all this talk of temperature compensating a Tbolt has anybody thought of programming up a PIC or AVR with associated circuitry to keep the beastie happy ? While Lady Heather is a grand master, I dont want to have a Windows PC permanently connected just for temperature stabilisation. A small chunk of linux based code might do, but a PIC or AVR would be better. LH in an AVR+LCD would be nice :) Or should I just put the Tbolt in a double enclosure, adjust time constants to suite and leave it at that ? regards Tim -- VK2XTT :: QF56if :: BMARC :: WIA :: AMSAT-VK :: AMSAT ___ 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] worth salvaging ?
Peter a couple of comments. Great pictures you can really see the technology and if the net connection wasn't so slow I would look at the eprom dates and such. I know Odetics, the company well. I think they are long gone or the goverment div survived so that suggests these are circa 1990-1994. I have been working with another time-nut to recover austron 2201a GPS receivers and unfortunately I seem to have come to the conclusion that we can not get the almanacs to update and will guess this would be the same issue with these potentially. But the odetics does look a bit newer. Drawing on the Austron I home brewed a down converter and that allowed me to at least discover various information. So the fact that you have one working a great step. I suspect however the OCXO may not be all that exciting as time-nuttery goes. On the down converters granted 10 are dead. But any details on the internals?? Regards Paul WB8TSL On Thu, Jan 27, 2011 at 7:35 PM, Chris Albertson albertson.ch...@gmail.comwrote: On Thu, Jan 27, 2011 at 3:54 PM, Pete Lancashire p...@petelancashire.com wrote: I'd like the lists opinion if saving the OCXO is worth puling of the board You mean is the OCXO worth your time to salvage it? I don't know but from those photos I see 100 parts that are worth my time to salvage. I look at those photos and see a goldmine of parts. I'd even salvage the little bead inductors and dip swiches The trick is not to worry at all about collateral damage on gear that is headed to the dumpster. If you think that way then salvage takes very little time. -- = Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ 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] Mass vs BTU Function
At 07:53 PM 1/27/2011, jimlux wrote... I did do some googling and found this interesting statement in Wikipedia Another way of stating this, is that the volume-specific heat capacity (volumetric heat capacity) of solid elements is roughly a constant. I'll admit that I'm prone to citing Wikipedia, but this is one case which clearly shows they're not authoritative. For just commonly available solid elements, there's a greater than 2:1 range. For time-nuts used to dealing with 10e-12 or smaller, that's no where near a constant. Below are numbers I posted a bit ago for hardware store stuff, and one could no doubt find a much greater range in compounds, especially if you ignore availability/cost: (substance) (specific heat) (density) (heat capacity?) ( ) (kJ/kg K) (g/ml^3)(kJ/l K) Al 0.91 2.7 2.5 Cu 0.39 9.96 3.9 Pb 0.13 11.36 1.5 Fe 0.46 7.87 3.6 H2O 4.2 1.0 4.2 ___ 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] power spectrum of hard limiter output
On 27/01/11 20:19, ehydra wrote: I found chapter Appendix 7A Analysis of interference in a hard limiter There is a half page with a couple of formulas. Not much, not practically oriented. Only idealized hard-limiters. I'm interested in SOFT-limiters! Jim's problem was with a hard-limiter so what I tossed his way was relevant to him. For soft-limiters, papers like this may be of assistance: http://webs.wichita.edu/depttools/depttoolsmemberfiles/ECE/Kwon%20Wireless/95Aug.pdf Hm. Does the writer seen a real working system once upon in time? Yes. What defines a working system is however covering a lot of systems and particulars of some systems can cover many books on its own without making other things irrelevant. 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] TBolt et al
On Thu, Jan 27, 2011 at 4:56 PM, Tim Tuck t...@skybase.net wrote: PPS to provide the ref for an embedded linux box to provide NTP. This will provide the 10Mhz and others as the master lock for my lab. A small chunk of linux based code might do, but a PIC or AVR would be better. Seems that you already have a Linux system connected 24x7 to the t-bolt. Why not run the controller on the NTP server? On my Linux based NTP server I have VMware installed and can bring up Win XP based GPS monitoring software. This all runs on a tiny little Atom CPU that does not draw enough power to require a fan on the CPU heat sink. It stays stone cold to the touch. Even running VMware and exporting the virtual machine's monitor over the network does not seem to bother NTP performance Actually I think little can be done to improve the T-Bolt over simply placing in a good location and not near a heater or AC vent and possibly in a vented box. -- = Chris Albertson Redondo Beach, California ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] power spectrum of hard limiter output
Magnus Danielson schrieb: On 27/01/11 20:19, ehydra wrote: I found chapter Appendix 7A Analysis of interference in a hard limiter There is a half page with a couple of formulas. Not much, not practically oriented. Only idealized hard-limiters. I'm interested in SOFT-limiters! Jim's problem was with a hard-limiter so what I tossed his way was relevant to him. I must say 'soft-limiter' is new to me, too! Sorry for pirate a thread. For soft-limiters, papers like this may be of assistance: http://webs.wichita.edu/depttools/depttoolsmemberfiles/ECE/Kwon%20Wireless/95Aug.pdf Interesting. 4dB below limit. Hm. Does the writer seen a real working system once upon in time? Yes. What defines a working system is however covering a lot of systems and particulars of some systems can cover many books on its own without making other things irrelevant. He he. We have many nonsense amateur info on the Web. Then many theoretical papers. A small gap between is useful for the practical oriented people. Unfortunately, this gap is just to slim. I find it more and more curious a working concept not to find in the I-net. I'm looking several weeks. Maybe wrong keywords. Thanks! - Henry ___ 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] TBolt et al
Heather started out as a AVR application on a MegaDonkey touch screen controller (http://www.mega-donkey.com) but I quickly came to the conclusion that it was much better suited to a dedicated $20 surplus laptop. You can rather easily extract the temperature controller code from the source code and port it to an AVR. ___ 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] power spectrum of hard limiter output
On 28/01/11 03:33, ehydra wrote: Magnus Danielson schrieb: On 27/01/11 20:19, ehydra wrote: I found chapter Appendix 7A Analysis of interference in a hard limiter There is a half page with a couple of formulas. Not much, not practically oriented. Only idealized hard-limiters. I'm interested in SOFT-limiters! Jim's problem was with a hard-limiter so what I tossed his way was relevant to him. I must say 'soft-limiter' is new to me, too! Sorry for pirate a thread. For soft-limiters, papers like this may be of assistance: http://webs.wichita.edu/depttools/depttoolsmemberfiles/ECE/Kwon%20Wireless/95Aug.pdf Interesting. 4dB below limit. Hm. Does the writer seen a real working system once upon in time? Yes. What defines a working system is however covering a lot of systems and particulars of some systems can cover many books on its own without making other things irrelevant. He he. We have many nonsense amateur info on the Web. Then many theoretical papers. A small gap between is useful for the practical oriented people. Unfortunately, this gap is just to slim. I find it more and more curious a working concept not to find in the I-net. I'm looking several weeks. Maybe wrong keywords. Well, have you considered what an AGC might do for you? It has been the traditional way of reducing the effect of signal level on phase-detector gain and hence on the loop gain. The hard-limiter text is to be seen in this context where the SNR steers the compression factor, i.e. change of loop gain. 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.
