[time-nuts] PICTIC chip 2nd round of orders, shipped!
Hi guys, Just a quick update. For those that sent me cash via paypal, the chips have all gone out with one exception (I'm waiting on an address from somebody).Expect to see them later this coming week. Sorry for the delay in getting them out. The chips have been sent in an anti-static plastic chip tube with a stopper at each end inside of a bubble wrap lined mailing envelope. Let me know if there is any damage or if there are any problems. Nobody reported any issues with the first round of orders so I suspect everything will be fine with this shipment. -Bob, N3XKB ___ 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] Timing Distribution in Mountainous Terrain
I believe the primary reasons for GPS receivers for the power industry is power line fault location. They use time tagging to measure disturbances to locate a fault and it's accuracy directly determines its resolution. On 9/11/2010 7:33 PM, jimlux wrote: Stan, W1LE wrote: If the odd harmonics were filtered out, would the zero crossing of the 60 (50) Hz fundamental be stable enough ? not to 30 ns Interestingly, one of the markets that Symmetricom/TrueTime/Datum sells into is GPS disciplined receivers used for power control. Power transmission is managed by controlling relative phases in the system, not to mention things like synchronizing generators. ___ 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] Timing Distribution in Mountainous Terrain
Stan, W1LE wrote: If the odd harmonics were filtered out, would the zero crossing of the 60 (50) Hz fundamental be stable enough ? not to 30 ns Interestingly, one of the markets that Symmetricom/TrueTime/Datum sells into is GPS disciplined receivers used for power control. Power transmission is managed by controlling relative phases in the system, not to mention things like synchronizing generators. ___ 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] HP 3575A Accuracy
Hi, I picked up an old HP 3575A I was wondering how accurate it is at compairing two 5 mhz or 10 mhz signals? Thanks Jeff ___ 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] OT: GPS simulator
Fellow time-nuts, While this is off-topic, I just wanted to drop a few lines... Spectracom/Pendulum (Pendulum Instruments is now parts of Spectracom) has released a 8 channel GPS simulator. It's an L1 C/A only thing, but I thought it may be useful for some of you guys to know about. It's designated GSG-54 and you find it on the Spectracom/Pendulum website. You can upload trajectories in NMEA format and ephimeris in RINEX. Ethernet, USB and GPIB interfaces. I haven't had it out for a test-drive, so I have no idea how good it is. 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] Timing Distribution in Mountainous Terrain
Hi Since the harmonics are locally generated, each site will see different crossings. The same is true of the local load impedance. Bob On Sep 11, 2010, at 5:54 PM, "Stan, W1LE" wrote: > If the odd harmonics were filtered out, would the zero crossing of the 60 > (50) Hz fundamental > be stable enough ? > > Thanks Stan,W1LE Cape Cod FN41sr > > > > > On 9/11/2010 5:08 PM, Bob Camp wrote: >> Hi >> >> You also have load dependent harmonic energy on there that messes up the >> zero crossings at the micro second level. >> >> Bob >> >> >> >> On Sep 11, 2010, at 3:45 PM, "Poul-Henning Kamp" wrote: >> >>> In message<8459b572-1428-4f6a-8375-afb4f7225...@cox.net>, "Thomas A. Frank" >>> wr >>> ites: >>> If so, being within 300 miles of each other suggests that they are most likely all on the SAME section of the grid, in which case the phase time of arrival of the electric power waveform should be constant between them (the zero crossing may not be perfectly aligned, but it should always be the same differential). >>> Won't work. Utility transformers have load-dependent parasitics >>> which mess this up. It is one of the biggest challenges in >>> doing "autonomous cell based grid control" and similar schemes. >>> >>> -- >>> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >>> p...@freebsd.org | TCP/IP since RFC 956 >>> FreeBSD committer | BSD since 4.3-tahoe >>> Never attribute to malice what can adequately be explained by incompetence. >>> >>> ___ >>> time-nuts mailing list -- time-nuts@febo.com >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >> ___ >> 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] Timing Distribution in Mountainous Terrain
If the odd harmonics were filtered out, would the zero crossing of the 60 (50) Hz fundamental be stable enough ? Thanks Stan,W1LE Cape Cod FN41sr On 9/11/2010 5:08 PM, Bob Camp wrote: Hi You also have load dependent harmonic energy on there that messes up the zero crossings at the micro second level. Bob On Sep 11, 2010, at 3:45 PM, "Poul-Henning Kamp" wrote: In message<8459b572-1428-4f6a-8375-afb4f7225...@cox.net>, "Thomas A. Frank" wr ites: If so, being within 300 miles of each other suggests that they are most likely all on the SAME section of the grid, in which case the phase time of arrival of the electric power waveform should be constant between them (the zero crossing may not be perfectly aligned, but it should always be the same differential). Won't work. Utility transformers have load-dependent parasitics which mess this up. It is one of the biggest challenges in doing "autonomous cell based grid control" and similar schemes. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ 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] Timing Distribution in Mountainous Terrain
On 09/11/2010 11:08 PM, Bob Camp wrote: Hi You also have load dependent harmonic energy on there that messes up the zero crossings at the micro second level. Not to speak about the highly shifting reactive load, which can shift both negative and positive... and mess about the transitions. 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] Timing Distribution in Mountainous Terrain
Hi You also have load dependent harmonic energy on there that messes up the zero crossings at the micro second level. Bob On Sep 11, 2010, at 3:45 PM, "Poul-Henning Kamp" wrote: > In message <8459b572-1428-4f6a-8375-afb4f7225...@cox.net>, "Thomas A. Frank" > wr > ites: > >> If so, being within 300 miles of each other suggests that they are >> most likely all on the SAME section of the grid, in which case the >> phase time of arrival of the electric power waveform should be >> constant between them (the zero crossing may not be perfectly >> aligned, but it should always be the same differential). > > Won't work. Utility transformers have load-dependent parasitics > which mess this up. It is one of the biggest challenges in > doing "autonomous cell based grid control" and similar schemes. > > -- > Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 > p...@freebsd.org | TCP/IP since RFC 956 > FreeBSD committer | BSD since 4.3-tahoe > Never attribute to malice what can adequately be explained by incompetence. > > ___ > time-nuts mailing list -- time-nuts@febo.com > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. > ___ 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] Timing Distribution in Mountainous Terrain
On 09/11/2010 08:24 PM, Ralph Smith wrote: On Sep 11, 2010, at 12:13 PM, Magnus Danielson wrote: On 09/11/2010 05:29 PM, jimlux wrote: If it's far enough in the future.. Hg ion traps have a lot of potential.. smaller, lower power, etc. than Cs Commercial availability is somewhat limited. that's for sure.. I think all the Hg ion traps are still laboratory curiosities.. but, 10 years from now? Sure, but that assumes his target deployment is 10 years ahead. Much closer than 10 years. The idea is to use existing or soon to be deployed infrastructure from the US ADS-B installation to also perform multilateration. I assumed within 1 or 2 years. This rules out waiting for commercialisation of new standards or new approaches on ADS-B receivers unless you control that process yourself. Yes, yes... I understood perfectly what you where describing and no doubt such a hint would be most useful, but it may not be applicable to his problem. The question is really if he has complete boxes to build with or can alter their design. Additional delta-channels is best handled in a combined receiver, as being done in many other similar heading receivers... such as GPS receivers with angular orientation such as used in airplanes and on ships. Multilateration can be performed with existing radios being deployed, deriving time synchronization from GPS. Future revision of radio specifications are possible, but are more likely to be incremental changes of existing design rather than more significant architectural changes. As expected. The concept for ADS-B multilateration is already set down, so the available parameters is really providing a timing system, algorithms of multilaterations and possibly aiding to sort things out. 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] Timing Distribution in Mountainous Terrain
In message <8459b572-1428-4f6a-8375-afb4f7225...@cox.net>, "Thomas A. Frank" wr ites: >If so, being within 300 miles of each other suggests that they are >most likely all on the SAME section of the grid, in which case the >phase time of arrival of the electric power waveform should be >constant between them (the zero crossing may not be perfectly >aligned, but it should always be the same differential). Won't work. Utility transformers have load-dependent parasitics which mess this up. It is one of the biggest challenges in doing "autonomous cell based grid control" and similar schemes. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 p...@freebsd.org | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Timing Distribution in Mountainous Terrain
Sites communicate via landline telco. If there are sufficient mutually visible networked sites to form a solution on an aircraft visible to stations not in the timing network that would work, and is one of the options we are studying. May it be assumed that the sites are on the regular electric grid? If so, being within 300 miles of each other suggests that they are most likely all on the SAME section of the grid, in which case the phase time of arrival of the electric power waveform should be constant between them (the zero crossing may not be perfectly aligned, but it should always be the same differential). Whether you can measure it to within 30 ns I'm not sure... Simpler thought - is the telco fiber? Could they drop a second dedicated one to link the sites? The notion that GPS will suddenly 'go away', without any other issues being present, is rather silly. That same solar flare that takes out GPS for all your sites is going to most likely render your other gear inoperative as well... Tom Frank, KA2CDK ___ 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] Timing Distribution in Mountainous Terrain
On Sep 11, 2010, at 12:13 PM, Magnus Danielson wrote: > On 09/11/2010 05:29 PM, jimlux wrote: If it's far enough in the future.. Hg ion traps have a lot of potential.. smaller, lower power, etc. than Cs >>> >>> Commercial availability is somewhat limited. >> >> that's for sure.. I think all the Hg ion traps are still laboratory >> curiosities.. but, 10 years from now? > > Sure, but that assumes his target deployment is 10 years ahead. Much closer than 10 years. The idea is to use existing or soon to be deployed infrastructure from the US ADS-B installation to also perform multilateration. > Yes, yes... I understood perfectly what you where describing and no doubt > such a hint would be most useful, but it may not be applicable to his > problem. The question is really if he has complete boxes to build with or can > alter their design. Additional delta-channels is best handled in a combined > receiver, as being done in many other similar heading receivers... such as > GPS receivers with angular orientation such as used in airplanes and on ships. Multilateration can be performed with existing radios being deployed, deriving time synchronization from GPS. Future revision of radio specifications are possible, but are more likely to be incremental changes of existing design rather than more significant architectural changes. Ralph ___ 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] HP 5086-7748 or similar mixer wanted
Try the HP_Aligent Yahoo Group. Dead SA mixers comes up all the time. Also, your unit might be repairable. There is a guy, Luis Cupido (?) in Portugal, who can bond in new diodes on some HP mixers. For alternatives, look at MiniCircuits. Good luck, -John === > Hi group, > > sorry I know its off topics but I'm desperately looking for a low-band > mixer > HP 5086-7748 for my HP 8594 Spectr.-Analyzer. > There are some offers at ebay but the price is totally out of budget > (~600-700USD). > > If the original typ isnt avaliable for amateurs budget I guess there must > be another > typ which possibly can be used?..!?? > > The mixer is a DC coupled one working from 9kHz to 2.9GHz at its RF input, > LO is from 3.9 - 6.8 GHz which gives a IF of 1 - 3.9 GHz. > > Anybody out there who has a usefull typ for sale ? > > Thanks in advance for looking into the part boxes. > > 73 > Peter, DG4EK > ___ > 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] HP 5086-7748 or similar mixer wanted
Hi group, sorry I know its off topics but I'm desperately looking for a low-band mixer HP 5086-7748 for my HP 8594 Spectr.-Analyzer. There are some offers at ebay but the price is totally out of budget (~600-700USD). If the original typ isnt avaliable for amateurs budget I guess there must be another typ which possibly can be used?..!?? The mixer is a DC coupled one working from 9kHz to 2.9GHz at its RF input, LO is from 3.9 - 6.8 GHz which gives a IF of 1 - 3.9 GHz. Anybody out there who has a usefull typ for sale ? Thanks in advance for looking into the part boxes. 73 Peter, DG4EK ___ 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] Timing Distribution in Mountainous Terrain
On 09/11/2010 05:29 PM, jimlux wrote: If it's far enough in the future.. Hg ion traps have a lot of potential.. smaller, lower power, etc. than Cs Commercial availability is somewhat limited. that's for sure.. I think all the Hg ion traps are still laboratory curiosities.. but, 10 years from now? Sure, but that assumes his target deployment is 10 years ahead. A problem with Hg ion traps would be ROHS, unless they can be exempted or assumed to be within the telco exempt, which would be a legal twist on the commercialisation aspect. And Cs or Rb don't have the same sorts of issues? No. http://en.wikipedia.org/wiki/Restriction_of_Hazardous_Substances_Directive Another aspect I have been wondering about is the trap hold-length, I think I recall that there was some issues relating to that... I think, though, that some sort of self calibrating array using the target of interest is a better scheme.. multiple receivers at each site separated by some distance. Getting milliradian angular resolution is a piece of cake. That moves the expense, and I don't think the available receivers have that option. They intend the spatial separation to be in kms and not m. I was thinking about changing the problem somewhat. Yes, but now you shifted from "time-support system of transciever boxes" to modifications of the boxes themselves or at least use multiple boxes for angle determination only (wasting much of the rest of the receiver structure). You'd have your stations separated by km, but each station has several receivers and can compare the phase of the signals. You can solve for range rate (Doppler) and angle (delta phase), and that can go into your position solution. (this is how we navigate spacecraft, after all, and it's also used for a variety of target tracking systems) Yes, yes... I understood perfectly what you where describing and no doubt such a hint would be most useful, but it may not be applicable to his problem. The question is really if he has complete boxes to build with or can alter their design. Additional delta-channels is best handled in a combined receiver, as being done in many other similar heading receivers... such as GPS receivers with angular orientation such as used in airplanes and on ships. 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] Timing Distribution in Mountainous Terrain
If it's far enough in the future.. Hg ion traps have a lot of potential.. smaller, lower power, etc. than Cs Commercial availability is somewhat limited. that's for sure.. I think all the Hg ion traps are still laboratory curiosities.. but, 10 years from now? A problem with Hg ion traps would be ROHS, unless they can be exempted or assumed to be within the telco exempt, which would be a legal twist on the commercialisation aspect. And Cs or Rb don't have the same sorts of issues? Another aspect I have been wondering about is the trap hold-length, I think I recall that there was some issues relating to that... I think, though, that some sort of self calibrating array using the target of interest is a better scheme.. multiple receivers at each site separated by some distance. Getting milliradian angular resolution is a piece of cake. That moves the expense, and I don't think the available receivers have that option. They intend the spatial separation to be in kms and not m. I was thinking about changing the problem somewhat. You'd have your stations separated by km, but each station has several receivers and can compare the phase of the signals. You can solve for range rate (Doppler) and angle (delta phase), and that can go into your position solution. (this is how we navigate spacecraft, after all, and it's also used for a variety of target tracking systems) Changing it from a rho-rho nav problem into a theta-theta problem (triangulation vs trilateration). The goal is to get target position to 10 meters, at a distance of, say, 20km, so you need angular measurements on the order of 0.5 milliradian (0.03 degree). Offhand, that might be easier than time to 30 ns. There are some significant issues here.. is the pulse long enough and enough power to make the required differential phase measurement, are there propagation issues (refraction, diffraction, multipath) that make milliradian precision impossible. The added hardware cost at each receiver site isn't much (compared to site costs, etc.) especially since you probably already need at least dual redundancy, so you can do N+1 redundancy, using 3 antenna/receivers at each site, using 2 of them at any given time. The wavelength at the transponder frequency is about 30cm, so with a moderate spacing of the receive antennas (say a meter), you'll get grating lobes and an angle ambiguity, but I think that could be resolved with the other information available (e.g. a coarse fix) 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] Timing Distribution in Mountainous Terrain
Don Latham wrote: jees, Bob, it's called a TDR - Original Message - From: "Bob Camp" To: "Discussion of precise time and frequency measurement" Sent: Friday, September 10, 2010 9:27 PM Subject: Re: [time-nuts] Timing Distribution in Mountainous Terrain Hi The assumption is that you can "bounce" a pulse off the far end of a single fiber or coax to read it's delay. Bob Actually, they don't use a TDR for this kind of thing.. you want to measure continuously in real time, so you propagate signals in both directions (at different frequencies) and look at phase differences, etc. With multiple fibers in the same jacket, you can assume that the fibers are the same, which makes life easier. On antenna ranges, with coax, the approach is similar, but you rely on a known mismatch at the probe. It's a fascinating metrology problem, especially if you want to actually "compensate" in real time, rather than just getting knowledge of the delay and using that in post processing. http://ipnpr.jpl.nasa.gov/progress_report/42-167/167C.pdf is a paper by Bob Tjoelker and others about how they do it for DSN. it has to be hotswappable, etc. there's some company in Colorado who makes the equipment, as I recall. ___ 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] Hg ion traps
Thank you Magnus. Bert -Original Message- From: Magnus Danielson To: time-nuts@febo.com Sent: Sat, Sep 11, 2010 8:12 am Subject: Re: [time-nuts] Hg ion traps On 09/11/2010 01:44 PM, ewkeh...@aol.com wrote: > I am intriged by the Hg ion trap. Can any one tell me what the exact 40.5 > GHz frequency is. Considering the C-field tweaking, which raises the frequency, this list will answer that question: http://rubidium.dyndns.org/~magnus/physics/hyperfine/ I am quite sure there is more references and values to be added, so please send me the articles and I will be happy to add them. For 199 Hg+ it is 40.50734799684159(14)(41) GHz. 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] Hg ion traps
On 09/11/2010 01:44 PM, ewkeh...@aol.com wrote: I am intriged by the Hg ion trap. Can any one tell me what the exact 40.5 GHz frequency is. Considering the C-field tweaking, which raises the frequency, this list will answer that question: http://rubidium.dyndns.org/~magnus/physics/hyperfine/ I am quite sure there is more references and values to be added, so please send me the articles and I will be happy to add them. For 199 Hg+ it is 40.50734799684159(14)(41) GHz. 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] Hg ion traps
I am intriged by the Hg ion trap. Can any one tell me what the exact 40.5 GHz frequency is. Thanks Bert Kehren ___ 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] Timing Distribution in Mountainous Terrain
It is my understanding that test equipment is exempt from all RoHS requirements. -Chuck Harris Magnus Danielson wrote: Commercial availability is somewhat limited. A problem with Hg ion traps would be ROHS, unless they can be exempted or assumed to be within the telco exempt, which would be a legal twist on the commercialisation aspect. ___ 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] Timing Distribution in Mountainous Terrain
On 09/10/2010 07:17 AM, jimlux wrote: Ralph Smith wrote: On Sep 9, 2010, at 8:01 PM, Rick Karlquist wrote: I would like to point out that the environmental sensitivities of the 5071A are unmeasureable, and the measurement threshold is far below 5.8E-14. I would estimate that the 5071A (and ONLY the 5071A among commercial clocks) could get the job done provided that you could compare its frequency to GPS to the stated accuracy. This would be using the 5071 as a secondary standard. You still need to deal with the short term stability of the 5071A, depending on your system needs. JPL uses H masers as flywheels. I would imagine the cost of a 5071A per radio station would make the check writers swallow hard, and adding an H Maser into the mix would really get their attention. Especially if you need redundancy. there's also the possibility mentioned earlier of using a lower quality standard at each station and flying (driving) a higher quality clock (5071) around often enough to keep them trued up. If it's far enough in the future.. Hg ion traps have a lot of potential.. smaller, lower power, etc. than Cs Commercial availability is somewhat limited. A problem with Hg ion traps would be ROHS, unless they can be exempted or assumed to be within the telco exempt, which would be a legal twist on the commercialisation aspect. Another aspect I have been wondering about is the trap hold-length, I think I recall that there was some issues relating to that... I think, though, that some sort of self calibrating array using the target of interest is a better scheme.. multiple receivers at each site separated by some distance. Getting milliradian angular resolution is a piece of cake. That moves the expense, and I don't think the available receivers have that option. They intend the spatial separation to be in kms and not m. 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] Thunderbolt power supply hookup
The separate power grounds available on the TBolt may be useful to improve performance. Someone, probably TVB, had comparative graphs of the TBolt with different power supplies. The 12v seems to be the sensitive one, it must power the analogue circuitry. By returning the sense lead of your 12V regulator to its own ground on the TBolt you should be able to provide cleaner power to the unit and get lower noise on its spectrum. cheers, Neville Michie On 11/09/2010, at 4:22 PM, Mark Spencer wrote: Thanks that all makes sense and power up went ok. - Original Message From: Hal Murray To: Discussion of precise time and frequency measurement n...@febo.com> Sent: Fri, September 10, 2010 11:04:21 PM Subject: Re: [time-nuts] Thunderbolt power supply hookup mspencer12...@yahoo.ca said: Would any one be able to point me towards a web site that shows the power supply pinout for the bare thunderbolt board (without the power supply board.) http://www.leapsecond.com/pages/tbolt/power.htm -- 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. ___ 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] Timing Distribution in Mountainous Terrain
On 09/10/2010 11:50 PM, jimlux wrote: Ralph Smith wrote: OK, stop me if this is really stupid. The initial site is in Colorado. Would it be possible to use WWV? In particular: 1) Lock a reference to the carrier of one of the WWV signals 2) Generate PPS off of WWV-locked reference 3) Periodically send difference of GPSDO PPS and WWV-locked PPS home, along with GPS lock indication 4) When GPS goes away do the math at home and correct for the timing drift of the GPSDO compared to WWV-locked reference I don't think a received WWV (or WWVB) signal is stable to 30ns... The critical aspect here is stable to 30 ns _relative_. I.e. common mode changes mostly cancels. I think it is problematic... the frequency of the carrier is too low. The vector sum of reflections may shift the group delay, and in this case the time error of such sums can be expected to be proportional to the wavelength. I would use one wavelength as the rule of thumb as long as it is not better quantified, and I would assume that individual changes can range that full range... Cheers, Magnus ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] Timing Distribution in Mountainous Terrain
jim...@earthlink.net said: > I seem to recall that the returned beam divergence was no narrower than the > incident beam divergence, so if you want a X km footprint on Earth, you > need a X km footprint on the Moon. Please let me know if you find that again. I poked around on the web and can't find anything that confirms my impression that they picked the size of the corner cubes to make sure the beam was large enough to cover the telescope motion due to the Earth's rotation. They are made out of fused silica. Thermal distortions are important. There are arrays from Apollo 11, 14, and 15. 11 and 14 are 100 cubes in a 10x10 array. 15 is 3x bigger. There is also an array of larger French cubes on Lunokhod, a Russian rover. There are brighter than Apollo 11 adn 14, even though the total reflecting area is smaller. http://www.physics.ucsd.edu/~tmurphy/apollo/lrrr.html (That's at night. During day, thermal distortion costs a factor of 30.) This page says the beam is 7 km dia on the moon due to atmosphere and 20 km back on the Earth due to diffraction. http://www.lpi.usra.edu/lunar/missions/apollo/apollo_11/experiments/lrr/ Dickey et al, 1994 is a good review article. http://www.physics.ucsd.edu/~tmurphy/apollo/doc/Dickey.pdf http://trs-new.jpl.nasa.gov/dspace/bitstream/2014/32452/1/94-0193.pdf (The second looks like an early version of the paper.) It confirms the beam diameters above. My calculation for the motion due to the Earth's rotation while the beam is in flight is 1or 2 km so 20 km easily covers that problem. There is a comment about correcting for something like the telescope not being in the center of the beam. Overall optical efficiency is about 1E-21. At 10 pulses per second with 1E19 photons each pulse, that's 1 photon every 10 seconds. A run is several hours. (The numbers get better over time.) In 1994, the RMS error was about 3 cm. A French station is getting a lot of good data. They have to consider solid tides and a zillion other details that I don't understand. (So add that one to the tides in solid rock list.) The Earth-moon distance is increasing by about 3.8 cm per year. I remember another story from long ago that one of the variables they had to add to their model was the location of the telescope on the surface of the Earth. The data fit better with the telescope a mile down the road from their coordinates from the USGS maps. I don't know if they ever tracked that down. -- There is a new Lunar Laser Ranging program called APOLLO. Apache Point Observatory Lunar Laser-ranging Operation http://www.physics.ucsd.edu/~tmurphy/apollo/apollo.html They are aiming for mm precision. They have a 3.5 meter telescope. Good geek data (graphs) here: http://www.physics.ucsd.edu/~tmurphy/apollo/first_range.html (Other stuff is good too, AKA time sink warning.) -- 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.
