[time-nuts] Did the FCC put LightSquared on ice?
The FCC has decided GPS is worth saving ... but not necessarily all current GPS receivers. http://www.aero-news.net/index.cfm?do=main.textpostid=1c898613-45b1-48a0-9d86-a767db2b017d -- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ 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] Did the FCC put LightSquared on ice?
On 11/08/11 08:03, Chuck Forsberg WA7KGX N2469R wrote: The FCC has decided GPS is worth saving ... but not necessarily all current GPS receivers. http://www.aero-news.net/index.cfm?do=main.textpostid=1c898613-45b1-48a0-9d86-a767db2b017d Root cause for interference is significantly changed dynamics requirements on the GPS receivers, as side-bands would become stronger. The dynamics has allowed for simple 1-bit or 1.5 bit receivers, where 1.5 bit receivers with separate level detection for AGC steering has better supression of CW signal than straight 1-bit. Much work went into few-bit ADC analysis in the early days, so the use is widespread. Using say 8-bit ADC would allow for the C/A code to de-correlate the signal further 30 dB down rather than letting the AGC be captured. That and filtering. One has to realize that the relative low interference have allowed many small and cheap designs to evolve, for the benefit of mobile phone use, tracking devices on packages etc. etc. Reducing civilian receivers resistance to jamming would also potentially reduce the effect of intentional jamming. Still, modern jamming techniques should not see much of such effect, so I don't think the green guys worry too much. 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] Why not TAI?
On Wed, 10 Aug 2011 16:35:11 +0200 cook michael michael.c...@sfr.fr wrote: If TAI is a paper clock, what else should be used if a strictly monotone time scale is needed? Do you have any specific application in mind? If you need an SI seconds rated scale, then you need something based on TAI. GPS time has a TAI second rate and is monotonic. But of course you would need a GPS receiver to access it. I don't have a specific application in mind. Just a general question on what should be used. But lets say i want to have a monotonic clock for a computer system to timestamp events precisely and unambigously. Yes, using GPS time (with or without going back to TAI) would be a probable solution. Are there any other time scales available that would fit that need? Attila Kinali -- The trouble with you, Shev, is you don't say anything until you've saved up a whole truckload of damned heavy brick arguments and then you dump them all out and never look at the bleeding body mangled beneath the heap -- Tirin, The Dispossessed, U. Le Guin ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Why not TAI?
Le 11/08/2011 08:57, Attila Kinali a écrit : On Wed, 10 Aug 2011 16:35:11 +0200 cook michaelmichael.c...@sfr.fr wrote: If TAI is a paper clock, what else should be used if a strictly monotone time scale is needed? Do you have any specific application in mind? If you need an SI seconds rated scale, then you need something based on TAI. GPS time has a TAI second rate and is monotonic. But of course you would need a GPS receiver to access it. I don't have a specific application in mind. Just a general question on what should be used. But lets say i want to have a monotonic clock for a computer system to timestamp events precisely and unambigously. Yes, using GPS time (with or without going back to TAI) would be a probable solution. Are there any other time scales available that would fit that need? Attila Kinali Well, there is : TT, Terrestrial Time, which is uniform (interval SI second), monotonic ; with an epoc of 00h 00m 00s 1 Jan 1977 TAI with a constant offset such that [TT] = [TAI] - 32.184s . Or more exotic: ET, Ephemeris Time, which is uniform and monotonic with a non SI second of 1/31566925,9747 of the tropical year of 1900. Julien Date is another , using SI second, but a numeric day label with an epoc of initial epoc defined as (UT) at midday on Monday Jan 1 4713 BC in the Julian calendar. It is measured in days and fractions with precision of about a millisecond and being numeric is so is easy to do calculations on. MJD , Modified Julien Date is the above -240,5 to keep the numbers down. This was recognised as a time scale by the IUT. I think it is now deprecated but is in common use. There are probably others. ___ 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] Why not TAI?
MJD , Modified Julien Date is the above -240,5 to keep the numbers down. This was recognised as a time scale by the IUT. I think it is now deprecated but is in common use. There are probably others. Oops, typo.. It should be UIT or ITU and not IUT and I forgot the cavet. In general any exotic scale would have to be either created from scratch or calculated from the available TAI based scales as none are transmitted. Many web pages of course will give nice clock animations. I recommend tvb's. ___ 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] Thunderbolt hardware revisions
All, The Label you are referring to is applied by the equipment mfgr, and has only a loose correlation to the vintage of the Trimble unit inside the case. The label has a bar code, a mfg serial number, the date the production bar code was issued, the Andrew/Grayson assembly part number (A002206.G1), and the revision letter of that assembly. Although I've never looked it up, I think Rev E changed the 3 dB splitter to a different model. If your case either has a small splitter attached, or 4 holes in the top cover where the scrapmonger ripped it off, it is probably a Rev E. That says nothing absolute about the vintage of the Thunderbolt inside. 73, geo - n4ua On Thu, Aug 11, 2011 at 12:54 AM, Ziggy zig...@pumpkinbrook.com wrote: Well, if it's any help, on my rev E unit with the 'coarse' temperature chip, there is a sticker on the top (near the power connector) with a bar code, a date (3/14/05) and the Rev E designation. There's also a series of numbers that could be a serial number and some other kind of rev designator but their significance is not clear. My Rev D unit with the 'fine' temperature chip has a similar sticker dated 12/16/03. Paul - K9MR On Aug 10, 2011, at 5:55 PM, Richard W. Solomon wrote: OK, now, how old is old enough ?? Where is the units date code located ? Hopefully, the seller knows (or even cares) where to find it. 73, Dick, W1KSZ -Original Message- From: Bob Camp li...@rtty.us Sent: Aug 10, 2011 9:59 AM To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Subject: Re: [time-nuts] Thunderbolt hardware revisions Hi The real question is what's the date code on the unit? If the rev E part is old enough to have the good thermometer chip in it - that's the one to get. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of David Garnier Sent: Tuesday, August 09, 2011 10:19 PM To: time-nuts@febo.com Subject: [time-nuts] Thunderbolt hardware revisions Hi, I'm brand new to the time-nut odessy thing so please bear with me. ;-) I'm in the market to buy a used Thunderbolt, I have found a vendor that's selling used Thunderbolt receivers and states one can have the choice of PCB revisions A, B or E. Does anyone have any specific info or determined the product history of these guys? Any information would be greatly appreciated. Thanks, Dave Garnier - wb9own ___ 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. ___ 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] Why not TAI?
The clock animations at http://www.leapsecond.com/java/gpsclock.htm are great, but one has to pay attention to the note at top, saying they are all based on your PC's clock, not actual time. If your pc is off 5 seconds, so will be all of those clocks. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of mike cook Sent: Thursday, August 11, 2011 1:02 AM To: time-nuts@febo.com Subject: Re: [time-nuts] Why not TAI? MJD , Modified Julien Date is the above -240,5 to keep the numbers down. This was recognised as a time scale by the IUT. I think it is now deprecated but is in common use. There are probably others. Oops, typo.. It should be UIT or ITU and not IUT and I forgot the cavet. In general any exotic scale would have to be either created from scratch or calculated from the available TAI based scales as none are transmitted. Many web pages of course will give nice clock animations. I recommend tvb's. ___ 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] Why not TAI?
Le 11/08/2011 16:25, Jose Camara a écrit : The clock animations at http://www.leapsecond.com/java/gpsclock.htm are great, but one has to pay attention to the note at top, saying they are all based on your PC's clock, not actual time. If your pc is off 5 seconds, so will be all of those clocks. Yes indeed. It was on looking at them yesterday that I discovered that my PC clock was 7 sec adrift. I had not restarted ntp after maintenance some weeks back and :( ___ 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] The future of UTC
Tony: I followed your suggestion and got both Seize the Daylight and Spring Forward from my local library. Seize the daylight : the curious and contentious story of daylight saving time / David Prerau / ISBN 1560256559 Spring forward : the annual madness of daylight saving / Michael Downing / ISBN 1582434956 Both have very interesting facts about the history of DST, but IMO Seize the Daylight is a much more enjoyable reading, following a script that better describes the events around each change (and has illustrations, too...). Things that some of us late 20th century creatures don't realize, like major city times, that would be off 35 minutes and only became a problem when trains started to connect them. Farmer's point of view, crusades for DST, war, etc. After reading them, I'm cured - no more posts defending, criticizing or suggesting amendments to DST. I just belong to the a certain DST 'religion' that would prefer we didn't have a 1hr step change twice a year, period. No desire to evangelize anyone in the other DST denominations, which is Quixotean task just as futile. It is too late now. Now if they propose changing the thermometer scales, to show 10 degrees higher in winter, 10 degrees lower in summer, to do similar mass hypnosis to save heating and a/c energy, I'll write my congresswoman. :-) Thanks for the book recommendation. Jose -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Tony Finch Sent: Monday, July 18, 2011 5:24 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] The future of UTC Jose Camara camar...@quantacorp.com wrote: I think before adding to the fire of UTC1, UTC7 etc. why not just abolish this silliness called Daylight Savings Time? If there is any benefit to it, just change business operating hours instead. If you want to know why your suggestion doesn't work, David Prerau has collected many many examples. http://www.seizethedaylight.com/ Tony. -- f.anthony.n.finch d...@dotat.at http://dotat.at/ Fair Isle: Northerly or northeasterly 4 or 5 increasing 5 or 6, but 6 or 7 in far west at first. Moderate or rough. Rain or showers. Moderate or poor. ___ 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] Thunderbolt hardware revisions
Hi Roughly mid 2004 is a reasonable point for the divide between the two thermometer chips. They apparently did not have a single magic date after which all boards got the newer / bad resolution chips. Replacement chips are available cheap, so switching the part out is an option. You also find boards that have been upgraded in terms of firmware and re-date coded. They may have been built in 2001, but the date code shows as 2004. Unless you can tear the beast open there is no perfect way to pick. Best bet - buy several and then sort them out. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of George Dubovsky Sent: Thursday, August 11, 2011 7:23 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Thunderbolt hardware revisions All, The Label you are referring to is applied by the equipment mfgr, and has only a loose correlation to the vintage of the Trimble unit inside the case. The label has a bar code, a mfg serial number, the date the production bar code was issued, the Andrew/Grayson assembly part number (A002206.G1), and the revision letter of that assembly. Although I've never looked it up, I think Rev E changed the 3 dB splitter to a different model. If your case either has a small splitter attached, or 4 holes in the top cover where the scrapmonger ripped it off, it is probably a Rev E. That says nothing absolute about the vintage of the Thunderbolt inside. 73, geo - n4ua On Thu, Aug 11, 2011 at 12:54 AM, Ziggy zig...@pumpkinbrook.com wrote: Well, if it's any help, on my rev E unit with the 'coarse' temperature chip, there is a sticker on the top (near the power connector) with a bar code, a date (3/14/05) and the Rev E designation. There's also a series of numbers that could be a serial number and some other kind of rev designator but their significance is not clear. My Rev D unit with the 'fine' temperature chip has a similar sticker dated 12/16/03. Paul - K9MR On Aug 10, 2011, at 5:55 PM, Richard W. Solomon wrote: OK, now, how old is old enough ?? Where is the units date code located ? Hopefully, the seller knows (or even cares) where to find it. 73, Dick, W1KSZ -Original Message- From: Bob Camp li...@rtty.us Sent: Aug 10, 2011 9:59 AM To: 'Discussion of precise time and frequency measurement' time-nuts@febo.com Subject: Re: [time-nuts] Thunderbolt hardware revisions Hi The real question is what's the date code on the unit? If the rev E part is old enough to have the good thermometer chip in it - that's the one to get. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of David Garnier Sent: Tuesday, August 09, 2011 10:19 PM To: time-nuts@febo.com Subject: [time-nuts] Thunderbolt hardware revisions Hi, I'm brand new to the time-nut odessy thing so please bear with me. ;-) I'm in the market to buy a used Thunderbolt, I have found a vendor that's selling used Thunderbolt receivers and states one can have the choice of PCB revisions A, B or E. Does anyone have any specific info or determined the product history of these guys? Any information would be greatly appreciated. Thanks, Dave Garnier - wb9own ___ 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. ___ 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] Why not TAI? (was: The future of UTC)
My Dual Scale Timekeeper will recover TAI from GPS by adding a constant 19 s offset, and it will track and serve out TAI in addition to UTR. What is usually meant by TAI is the single extremely accurate, post-processed, paper time-scale managed by BIPM. TAI itself is derived from EAL and other inputs. TAI is the basis of UTC. No one has copyright on these acronyms and confusion can result when TAI is used to mean too many things. You can recover TAI from a GPS timing receiver by adding 19 seconds in the same crude way I can recover TAI by looking at the big clock outside the bank building and adding 7 hours and 34 seconds. Or by taking a PC clock and making my web page: http://leapsecond.com/java/gpsclock.htm. Yes, these look like TAI. But are they really TAI? Or are they all just another 6-digit hour:minutes:second clock display that tries to be close to what TAI would look like if one had access to it? A question to ask is how many nanoseconds, or milliseconds, or even seconds does your TAI clock have to be off before you can't rightfully call it TAI anymore? I don't have an answer. Naming ambiguity is even worse with UTC. You can't have a clock at home that is UTC. What you can have at home is a WWVB clock that closely follows UTC(NIST) or a GPS display clock that closely follows UTC(USNO). But how close is left undefined. If you put the GPS receiver in holdover mode, when does the display stop being UTC? Most Windows PC's at home are off by seconds. Does that mean most of them are running UT1 instead of UTC? What is missed in many discussions about time scales is intent or implied accuracy. If I manually adjust my Pacific Daylight Time wrist-watch ahead by 7 hours does it then become a UTC watch? If I further adjust it by 0.3 seconds can I now claim it's showing UT1? Can I even wear a wrist-watch that displays TAI? Is it possible for any clock with analog hands to display UTC? What we call a time scale is more than just an integer offset. I'm working on a paper that explores all these issues. /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] The future of UTC
Jose Camara camar...@quantacorp.com wrote: Thanks for the book recommendation. I'm enormously pleased you enjoyed it. Sounds like you had the same unexpected reaction that I did! Tony. -- f.anthony.n.finch d...@dotat.at http://dotat.at/ Northwest FitzRoy, Sole, Lundy, Fastnet: Westerly or southwesterly 4 or 5. Moderate or rough. Occasional rain. Good, occasionally poor. ___ 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] Why not TAI? (was: The future of UTC)
On 11/08/11 18:20, Tom Van Baak wrote: My Dual Scale Timekeeper will recover TAI from GPS by adding a constant 19 s offset, and it will track and serve out TAI in addition to UTR. What is usually meant by TAI is the single extremely accurate, post-processed, paper time-scale managed by BIPM. TAI itself is derived from EAL and other inputs. TAI is the basis of UTC. No one has copyright on these acronyms and confusion can result when TAI is used to mean too many things. You can recover TAI from a GPS timing receiver by adding 19 seconds in the same crude way I can recover TAI by looking at the big clock outside the bank building and adding 7 hours and 34 seconds. Or by taking a PC clock and making my web page: http://leapsecond.com/java/gpsclock.htm. Yes, these look like TAI. But are they really TAI? Or are they all just another 6-digit hour:minutes:second clock display that tries to be close to what TAI would look like if one had access to it? A question to ask is how many nanoseconds, or milliseconds, or even seconds does your TAI clock have to be off before you can't rightfully call it TAI anymore? I don't have an answer. Naming ambiguity is even worse with UTC. You can't have a clock at home that is UTC. What you can have at home is a WWVB clock that closely follows UTC(NIST) or a GPS display clock that closely follows UTC(USNO). But how close is left undefined. If you put the GPS receiver in holdover mode, when does the display stop being UTC? Most Windows PC's at home are off by seconds. Does that mean most of them are running UT1 instead of UTC? What is missed in many discussions about time scales is intent or implied accuracy. If I manually adjust my Pacific Daylight Time wrist-watch ahead by 7 hours does it then become a UTC watch? If I further adjust it by 0.3 seconds can I now claim it's showing UT1? Can I even wear a wrist-watch that displays TAI? Is it possible for any clock with analog hands to display UTC? What we call a time scale is more than just an integer offset. I'm working on a paper that explores all these issues. How close you need to get depends on your application and it's needs. If you need to be within +/- 1 us, then turning off your outputs when you expect to have drifted away 1 us from where the time-scale should be is resonable, this is a confidence interval thing. Whichever time-scale you try to realize, you will have biases, deviations and additional noise uncertainty. How much you tolerate and the requirement on hold-over depends on your application. It should not be very surprising. The concept of hold-over seems to be not as well covered in the literature as you would expect. 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] Did the FCC put LightSquared on ice?
Under FCC rules, receivers have an economic lifetime, so if one makes changes slowly enough, it's OK. (I worked for the FCC in the 1970s.) From: Chuck Forsberg WA7KGX N2469R c...@omen.com To: ExTek gatesja-l...@eskimo.com, time-nuts time-nuts@febo.com Date: 08/11/2011 02:04 AM Subject:[time-nuts] Did the FCC put LightSquared on ice? Sent by:time-nuts-boun...@febo.com The FCC has decided GPS is worth saving ... but not necessarily all current GPS receivers. http://www.aero-news.net/index.cfm?do=main.textpostid=1c898613-45b1-48a0-9d86-a767db2b017d -- Chuck Forsberg WA7KGX N2469R c...@omen.com www.omen.com Developer of Industrial ZMODEM(Tm) for Embedded Applications Omen Technology Inc The High Reliability Software 10255 NW Old Cornelius Pass Portland OR 97231 503-614-0430 ___ 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. inline: graycol.gifinline: ecblank.gif___ 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] Oscillator Buddy
What may make a nice little nut-project is a simple PIC processor type Oscillator Buddy circuit that would reduce the effects of environmental and time caused oscillator frequency drift errors using the oscillator's EFC analog input. What makes a nice Time-Nut Oscillator candidate for this project is one that is repeatable AND predicable. I am continually ageing and testing several good oscillators including single and dual oven HP10811s and LPRO Rb to find the most predicable repeatable ones. On these type of selected Oscillators, after minimizing the frequency uncertainty errors due to basic things like power supply effects and RF load changes and keeping them in a reasonable stable environment, the main errors I see are: 1) ADEV noise at tau = 1sec for OXCOs and at 100 sec for RBs (typical range is from 0.2e-12 to 2e-12) 2) Temperature coefficient (the typical range is from +- 1e-13 to 1e-10 per degC) 3) Ageing rate (typical range is + - 1e-13 to 1e-10 per day) 4) Barometric pressure (Typical effect TBD) I have found it is possible to reduce the environment and time caused freq drift errors by 10 to 1 or more on some of the better selected oscillators using open loop correction techniques. Disciplining the Osc with GPS in a closed loop (aka Tbolt GPSDO) is the typical and most effective way to reduce the effects of #2, 3, 4 above, but that does have some limitations and the better the disciplined osc is open loop then the better the closed loop results. Any thoughts and comments on an Oscillator Buddy project. ws ___ 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] Oscillator Buddy
Hi Warren: I looked into using a PIC to make a GPSO and there are two problems: (1) is the number of bits you can get in the D/A converter. The best solution I've seen is used in the Quantic Q5200 GPS receiver which has what amounts to an internal GPSDO with 48 bits in the oscillator drive. It's in their US Patent 5440313 (link on Q5200 web page). http://www.prc68.com/I/Q5200.shtml (2) Noise on the control voltage. When I was at HP/Agilent a neighboring engineer was THE man on their 4352 VCO/PLL tester. The D/A converter in it and in the combo boxes (4395 4396 among others) not only had a lot of bits it was also extremely quiet. Getting both of these is far from simple. http://www.prc68.com/I/4395A.shtml Have Fun, Brooke Clarke http://www.PRC68.com http://www.End2PartyGovernment.com/ WarrenS wrote: What may make a nice little nut-project is a simple PIC processor type Oscillator Buddy circuit that would reduce the effects of environmental and time caused oscillator frequency drift errors using the oscillator's EFC analog input. What makes a nice Time-Nut Oscillator candidate for this project is one that is repeatable AND predicable. I am continually ageing and testing several good oscillators including single and dual oven HP10811s and LPRO Rb to find the most predicable repeatable ones. On these type of selected Oscillators, after minimizing the frequency uncertainty errors due to basic things like power supply effects and RF load changes and keeping them in a reasonable stable environment, the main errors I see are: 1) ADEV noise at tau = 1sec for OXCOs and at 100 sec for RBs (typical range is from 0.2e-12 to 2e-12) 2) Temperature coefficient (the typical range is from +- 1e-13 to 1e-10 per degC) 3) Ageing rate (typical range is + - 1e-13 to 1e-10 per day) 4) Barometric pressure (Typical effect TBD) I have found it is possible to reduce the environment and time caused freq drift errors by 10 to 1 or more on some of the better selected oscillators using open loop correction techniques. Disciplining the Osc with GPS in a closed loop (aka Tbolt GPSDO) is the typical and most effective way to reduce the effects of #2, 3, 4 above, but that does have some limitations and the better the disciplined osc is open loop then the better the closed loop results. Any thoughts and comments on an Oscillator Buddy project. ws ___ 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] Trimble T-Bolt Power Supply Question
Has anyone used the Cisco Systems Power Supply (34-0874-01) to power the Trimble Thunderbolt ? I know there are other supplies out there, but I have one in the Junque Boxe and am curious if anyone has used one and how it performed. Thanks, Dick, W1KSZ ___ 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] Frequency Comparator Ideas needed
Hi All, I could clairify things a little. My event of interest is basically a fast frequency shift of a signal that drifts between 1800 and 2600Mhz. There is slow drift of this signal of many hundreds of Mhz, with fast frequency shifts of approximatley +/- 150Khz. I believe that the 150Khz shifts are nearly instantaneous, but currently have no way to measure exactly how fast they occur. Slow drifts are corrected for by a loop in the down converter. Currently there is a first down conversion stage to ~900Mhz. This is then down converted again to an arbitrary frequency band (50Mhz in this example, but this could be moved from ~10Mhz to 200Mhz or greater). Obviously it would be advantageous to keep the low frequency band as high as possible, at least when trying to determine when the frequency shifts occur with any digital detectors. Probably for any analog detectors also. Bob, Obviously I'd like to get as close to the real zero crossing as possible, but I'm sure I don't need 0.6pS. If I could tell if the signal was within maybe +/- 15 or 20Khz, it may be acceptable. I could always double the frequency then down convert to increase the deviation. Basically, I have another timing device that will record every single event within 5nS, as long as they don't exceed ~1e6 events per second. That's the unit I'll feed the signal into, and what I need to keep happy. I did just learn about Gilbert cell mixer that works from DC to 500Mhz yesterday. I didn't realize they were available with that wide of a bandwidth. With this part as an option, it may be possible to do a quadrature detection around the several hundred Mhz range. That way subsequent low pass filters can have fairly high bandwidth. I'm sure the results here will probably be noisy, but maybe still acceptable??? However, I'd still like to it digitally if possible. Maybe even adding a second VCO with high modulation bandwidth to use a PLL with to track the input signal. Maybe then a phase detector comparing that PLL output and the reference signal and some high speed digital processing could prove useful. Not sure tho, still need to think about that. Probably would end up needing some multi Ghz flip flops to make that work... Ultimately this may not be possible digitally, but I thought if anyone here knew of anything it would be here... Thanks all! Dan ___ 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] Frequency Comparator Ideas needed
Seems to me like an HP 5335A is well suited to this task. It measures frequency in the required range and has adjustable gate times so you can get updates at the rate you need. These sell on eBay for as low as $200 and from other placed for $600. They have signal conditioning, and a computer interface all in one rack mount box. Accuracy is better then you say you need. On Thu, Aug 11, 2011 at 1:10 PM, Dan Kemppainen d...@irtelemetrics.comwrote: Hi All, I could clairify things a little. My event of interest is basically a fast frequency shift of a signal that drifts between 1800 and 2600Mhz. There is slow drift of this signal of many hundreds of Mhz, with fast frequency shifts of approximatley +/- 150Khz. I believe that the 150Khz shifts are nearly instantaneous, but currently have no way to measure exactly how fast they occur. Slow drifts are corrected for by a loop in the down converter. Currently there is a first down conversion stage to ~900Mhz. This is then down converted again to an arbitrary frequency band (50Mhz in this example, but this could be moved from ~10Mhz to 200Mhz or greater). Obviously it would be advantageous to keep the low frequency band as high as possible, at least when trying to determine when the frequency shifts occur with any digital detectors. Probably for any analog detectors also. 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] Oscillator Buddy
Brooke One simple way I'veused to eliminate the two problems you brought up is by Greatly restricting the tuning effect of the Dac voltage. Only big downside is you then may have to manually reset the nominal Osc freq every once in a while if the Dac gets near a limit. With a little thought an 8 bit Dac is more than enough to make a great GPSDO out of a good Osc, as long as the Osc also has a course freq tuning method like the HP 10811 does. But what I was suggesting is not a GPSDO, but an open loop freq compensator. Simplified example: Make the analog output of the PIC equal to (K1 times measured temperature) + (K2 times lapsed time) With that, K1 can be used to cancel the Osc tempCoef and K2 the daily ageing rate. Having fun, always thanks ws ** Hi Warren: I looked into using a PIC to make a GPSO and there are two problems: (1) is the number of bits you can get in the D/A converter. The best solution I've seen is used in the Quantic Q5200 GPS receiver which has what amounts to an internal GPSDO with 48 bits in the oscillator drive. It's in their US Patent 5440313 (link on Q5200 web page). http://www.prc68.com/I/Q5200.shtml (2) Noise on the control voltage. When I was at HP/Agilent a neighboring engineer was THE man on their 4352 VCO/PLL tester. The D/A converter in it and in the combo boxes (4395 4396 among others) not only had a lot of bits it was also extremely quiet. Getting both of these is far from simple. http://www.prc68.com/I/4395A.shtml Have Fun, Brooke Clarke http://www.PRC68.com http://www.End2PartyGovernment.com/ WarrenS wrote: What may make a nice little nut-project is a simple PIC processor type Oscillator Buddy circuit that would reduce the effects of environmental and time caused oscillator frequency drift errors using the oscillator's EFC analog input. What makes a nice Time-Nut Oscillator candidate for this project is one that is repeatable AND predicable. I am continually ageing and testing several good oscillators including single and dual oven HP10811s and LPRO Rb to find the most predicable repeatable ones. On these type of selected Oscillators, after minimizing the frequency uncertainty errors due to basic things like power supply effects and RF load changes and keeping them in a reasonable stable environment, the main errors I see are: 1) ADEV noise at tau = 1sec for OXCOs and at 100 sec for RBs (typical range is from 0.2e-12 to 2e-12) 2) Temperature coefficient (the typical range is from +- 1e-13 to 1e-10 per degC) 3) Ageing rate (typical range is + - 1e-13 to 1e-10 per day) 4) Barometric pressure (Typical effect TBD) I have found it is possible to reduce the environment and time caused freq drift errors by 10 to 1 or more on some of the better selected oscillators using open loop correction techniques. Disciplining the Osc with GPS in a closed loop (aka Tbolt GPSDO) is the typical and most effective way to reduce the effects of #2, 3, 4 above, but that does have some limitations and the better the disciplined osc is open loop then the better the closed loop results. Any thoughts and comments on an Oscillator Buddy project. ws ___ ___ 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] Frequency Comparator Ideas needed
If this is not a board design situation, but just a lab setup to measure and characterize it, the 53310A could also work, giving a plot of frequency x time, right on the instrument. GPIB can bring data out, too. They go for $300 to $1500 on eBay. -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Chris Albertson Sent: Thursday, August 11, 2011 1:29 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Frequency Comparator Ideas needed Seems to me like an HP 5335A is well suited to this task. It measures frequency in the required range and has adjustable gate times so you can get updates at the rate you need. These sell on eBay for as low as $200 and from other placed for $600. They have signal conditioning, and a computer interface all in one rack mount box. Accuracy is better then you say you need. On Thu, Aug 11, 2011 at 1:10 PM, Dan Kemppainen d...@irtelemetrics.comwrote: Hi All, I could clairify things a little. My event of interest is basically a fast frequency shift of a signal that drifts between 1800 and 2600Mhz. There is slow drift of this signal of many hundreds of Mhz, with fast frequency shifts of approximatley +/- 150Khz. I believe that the 150Khz shifts are nearly instantaneous, but currently have no way to measure exactly how fast they occur. Slow drifts are corrected for by a loop in the down converter. Currently there is a first down conversion stage to ~900Mhz. This is then down converted again to an arbitrary frequency band (50Mhz in this example, but this could be moved from ~10Mhz to 200Mhz or greater). Obviously it would be advantageous to keep the low frequency band as high as possible, at least when trying to determine when the frequency shifts occur with any digital detectors. Probably for any analog detectors also. 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.
[time-nuts] Oscillator Buddy
Warren, I agree with other responders that a closed loop approach to OCXO minding is feasible using a simple micro and D-A. I designed a system which has as its main focus low ADev and reasonably good frequency accuracy, without necessarily requiring the tight timing of a commercial GPSDO or the use of high resolution D-A. You might consider my system 'loose' control, as it relies on the OCXO being pretty good in the first place. It just corrects for long term effects such as ageing. What I came up with may be helpful. Essentially it phase locks the OCXO to GPS 1pps, but does so with extremely long integration times (hours), and with modest gain, so provided the OCXO is not subject to sudden temperature extremes or has an excessive ageing rate, will provide good control. As others have suggested, if you limit the control range (in my case I have a manual coarse setting) you can achieve very good closed-loop control with limited D-A resolution. I used 15 bit PWM, using a 12-bit timer and 3 bits of dither, providing a range of under 1ppm and a step size of about 3e-11. The system has no predictive capability, but does achieve (with a good OCXO) quite good holdover performance. By studying the control voltage over the last year, I've determined by extrapolation that manual intervention (coarse adjustment) will be unlikely within 10 years. I used a small AVR processor, did all the counting and maths in the processor, and operated the analog circuitry from the internal reference in the OCXO, resulting in very good thermal performance. The design is described in some detail at http://www.qsl.net/zl1bpu/MICRO/SIMPLE/SimpleGPS.htm. Regards, Murray Greenman ___ 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] Frequency Comparator Ideas needed
Hi If you need to know when the shifts occur in tens of ns, that significantly limits what you can do. Getting 20 million readings a second is tough. If this is an off the air signal, it's noise is probably not good enough for you to estimate it accurately enough in that time frame. If this is FSK, then modulation theory gets in the way a bit. 150KHz instantaneous shifts generate a lot of energy at the shift point. You also need to worry about dynamic range in addition to signal to noise. How about a simple FM discriminator with a bandwidth around 10 MHz and a center at 50 MHz?. Feed the output into an A/D and take it from there. It's probably as good as anything else you could do. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Dan Kemppainen Sent: Thursday, August 11, 2011 4:11 PM To: time-nuts@febo.com Subject: Re: [time-nuts] Frequency Comparator Ideas needed Hi All, I could clairify things a little. My event of interest is basically a fast frequency shift of a signal that drifts between 1800 and 2600Mhz. There is slow drift of this signal of many hundreds of Mhz, with fast frequency shifts of approximatley +/- 150Khz. I believe that the 150Khz shifts are nearly instantaneous, but currently have no way to measure exactly how fast they occur. Slow drifts are corrected for by a loop in the down converter. Currently there is a first down conversion stage to ~900Mhz. This is then down converted again to an arbitrary frequency band (50Mhz in this example, but this could be moved from ~10Mhz to 200Mhz or greater). Obviously it would be advantageous to keep the low frequency band as high as possible, at least when trying to determine when the frequency shifts occur with any digital detectors. Probably for any analog detectors also. Bob, Obviously I'd like to get as close to the real zero crossing as possible, but I'm sure I don't need 0.6pS. If I could tell if the signal was within maybe +/- 15 or 20Khz, it may be acceptable. I could always double the frequency then down convert to increase the deviation. Basically, I have another timing device that will record every single event within 5nS, as long as they don't exceed ~1e6 events per second. That's the unit I'll feed the signal into, and what I need to keep happy. I did just learn about Gilbert cell mixer that works from DC to 500Mhz yesterday. I didn't realize they were available with that wide of a bandwidth. With this part as an option, it may be possible to do a quadrature detection around the several hundred Mhz range. That way subsequent low pass filters can have fairly high bandwidth. I'm sure the results here will probably be noisy, but maybe still acceptable??? However, I'd still like to it digitally if possible. Maybe even adding a second VCO with high modulation bandwidth to use a PLL with to track the input signal. Maybe then a phase detector comparing that PLL output and the reference signal and some high speed digital processing could prove useful. Not sure tho, still need to think about that. Probably would end up needing some multi Ghz flip flops to make that work... Ultimately this may not be possible digitally, but I thought if anyone here knew of anything it would be here... Thanks all! Dan ___ 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] Why not TAI? (was: The future of UTC)
On Thu, Aug 11, 2011 at 03:03, Mike S mi...@flatsurface.com wrote: And who, exactly, says don't use TAI? Is this documented somewhere, or do you have to be a member of the secret time society which wants to control it all? For starters, we[1] are not called the Secret Time Society. That would be a dead giveaway, wouldn't it? [1] I am not sure of the we part, as I have not met or even heard of any other members, but that is probably because we are super-secret. -- Sanjeev Gupta +65 98551208 http://www.linkedin.com/in/ghane ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
