Re: [time-nuts] Housing LPRO and Thunderbolt together
Bill, On 04/24/2011 02:50 AM, WB6BNQ wrote: Magnus, I just cannot believe you are disagreeing with me ! However, I still stand behind my statement. Considering the two mechanisms, the quartz blank seldom fail in a proper design. Whereas the Rubidium is guaranteed to fail as you have admitted. But you do have a point that the Rubidium can be revived with a good degree of success. The quartz blank, if fractured, is no more period. Well, there is a huge difference between failure as in need total replacement and failure as in needing mild service. Hence, I wanted us to separate the issue into not two but three categories. The reason is that for too long it has been seen as a (non-restorable) wear mechanism, as if the rubidium was lost. It's not lost, it is just relocated inside the assembly in a way that makes the lamp having problems. These can be solved. So, to make my point clearer we have these three categories: 1) Fundamental wear, will fail in approx X hours from leaving factory - Caesium clocks has this mechanism in several places, such as mass-spectrometer, ion pump, caesium source and just general caesium pollution. 2) Relative wear, will fail in approx X hours, but can be revived (possibly multiple times) for additional Y hours of operation - Rubidium and hydrogen clocks has this mechanism. Most rubidium clocks can operate for about 10 years and then be revived. Hydrogen clocks require hydrogen refill and replacement of ion pump. 3) Slow material shift, will operate for very long, but may drift out of useful range - Good crystal oscillators can belong to this range. They may continue to drift and oscillate, but they may drop out of useful range as they no longer can be pulled into the useful range of frequencies needed for the application. The crystal blank etc. may not fail as such, but it can become useless never the less. So, I mostly disagree with your grouping of 12 into one group and to some degree of the long term aspect of group 3. The division is not as sharp as you claim it to be, and I could come up with even more groups if I where to add lower quality oscillators in it... and start to consider electronic design issues... So I don't think we are in wild disagreement really, I think we only need to talks things over to come to a mutual agreement. It's about weighing in sufficient aspects and knowledge. We all contribute to that here. And of course we are ignoring all the standard electronic parts, etc., and only talking about the primary mechanisms. Indeed. 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] Housing LPRO and Thunderbolt together
I like the Schroff ones, in aluminium or steel: http://es.farnell.com/jsp/search/browse.jsp?N=51+1000845Ntk=gensearch_001Ntt=schroff+1uNtx=mode+matchallpartial http://es.farnell.com/jsp/search/browse.jsp?N=51+1006552Ntk=gensearch_001Ntt=schroff+1uNtx=mode+matchallpartial They are available in US through Newark Regards, Javier El 23/04/2011 02:42, brent evers escribió: Somewhat related to this, someone posted a link for 1U chassis a while back. I thought I saved the link, but can't find it, and since the text of posts can't be searched from the archives, can't find mention of it that way either. If anyone has a decent source for 1U chassis that I could mount a pair of tbolts in, I would appreciate it. These were generic 1U rackmount chassis - not 'server' chassis with a bunch of preplanned holes. Brent On Fri, Apr 22, 2011 at 5:37 PM, WB6BNQwb6...@cox.net wrote: Hi Pete, As Bob, K6RTM, pointed out the Thunderbolt and the Rubidium are two different animals all together. True, you can treat a Rubidium like it was a normal crystal oscillator, but it is not the same. The Rubidium has a definite life span, the more you run it the less the life. A high quality crystal oscillator, on the other hand, just gets better the longer you leave it on. Aside from nominal electrical component failures, the crystal blank in a properly designed circuit has no short term failure mechanism and will last for decades with constant applied power. The Rubidium’s life span is, at best, 10 years. The question is how long was it running before you got it ? A high quality crystal oscillator has excellent short term specs but does have drift and aging functions that severely limit its use for long term purposes. Long term meaning more than a few hours for the best. That is where the Rubidium oscillator takes over as its drift function is measured in days to a month or more. For high quality measurements, the crystal excels for measurement times of less than 10 seconds, as the Rubidium is noisier in that time frame. That is, for taking readings on a one second to second basis, such as with a high resolution time interval counter, the crystal excels. However, if the period of the measurement is longer, then the Rubidium would be a better choice. For portable purposes the Rubidium also excels as its retrace is much better than a crystal oscillator. You also do not need to wait the thirty to sixty days for the crystal to stabilize. The Rubidium will be very close to its original set point in about 20 minutes. Adding GPS to mix has its own issues. First, you need to know the coordinates precisely or spend a couple of days getting a damn good fix. The GPS is quite noisy in the short term and the oscillator that is steered by the GPS has that noise show up in its output. That is mitigated by having a high quality crystal oscillator where the GPS control loop seldom makes corrections; perhaps once an hour or more. That is how the Thunderbolt works and depending upon its internal crystal oscillator, it may possibly be tweaked to perform better then the standard factory settings. As for use, it all depends upon what and how you’re making measurements. With a nominal 8 or 9 digit counter, for example, you may not notice all of the above issues because they are typically beyond the resolution of the equipment in most cases. In other measurement processes it may be of major concern. As for your project boxes, I would use the rack mounted box to house the Thunderbolt, distribution amps and perhaps a couple of other oscillators (like the hp 10811) along with quality power sources. Because crystal oscillators like a constant operating condition, do consider battery power for the lab to handle those occasional mains power drops. I would use the portable box for the Rubidium oscillator and include a battery option depending upon your intent. The emphasis should be to have very quiet and stable power supplies for both projects. Even batteries have a fair amount of noise so make the mains power (and battery) voltage high enough to allow for running a quality regulation circuit. My two cents ! 73BillWB6BNQ g4...@btopenworld.com wrote: I have a dilemma and wish to access the collective wisdom of the group to advise a solution. I am building a clock generator based on a Thunderbolt. I have an LPRO and would also locate this in the same enclosure. I will also add a distribution amp and a divide chain in due course. The ultimate purpose of the set up is to provide a self contained clock generator set for my other test equipment, and also an experimental workstation for Rubidium and GPS disciplined experiments. Most of my other equipment is for 19-inch rack mounting. I have two potential solutions for housing the timing kit: 1. An old dismantled HP 4U scope chassis which will fit in with my other equipment physically, and can be racked if necessary. The PSU would have to
Re: [time-nuts] Housing LPRO and Thunderbolt together
Bill's comments made me ruminative. Because there seem to be different informations circulating about the possibility to discipline Rubidium Oscillators, their phase stability and lifetime. I would like to have it precised or corrected. Dated 22.04.2011 23:37, WB6BNQ wrote: True, you can treat a Rubidium like it was a normal crystal oscillator, but it is not the same. The Rubidium has a definite life span, the more you run it the less the life. A high quality crystal oscillator, on the other hand, just gets better the longer you leave it on. Aside from nominal electrical component failures, the crystal blank in a properly designed circuit has no short term failure mechanism and will last for decades with constant applied power. The Rubidium’s life span is, at best, 10 years. The question is how long was it running before you got it ? For high quality measurements, the crystal excels for measurement times of less than 10 seconds, as the Rubidium is noisier in that time frame. That is, for taking readings on a one second to second basis, such as with a high resolution time interval counter, the crystal excels. What I not understood (yet) is: Why shall RbDOCXOs be worse in short term stability terms than good OXCOs? Why shall the output of a HP10811A or a similar high grade OCXO degrade when properly disciplined by a RbO or a GPS Receiver or both combined? Some RbOs do use in fact an OCXO as controlled oscillator element. A good example is the PRS10 from SRS with a very informative manual containing good informations and functional schemes. Its stability of about 5 × 10−12 at Tau 10s and SSB-Phase Noise of −130 dBc/Hz (10 Hz), Short Term Stability of 1 × 10−11 (10 s) sounds good. As it has an analog 0-5V Frequency Adjust and a 1 PPS input it can be well controlled via GPS I think. Why not try to exchange the Trimble's Thunderbolt OCXO with an external 10811A shown by John Miles or even with a PRS10? The Thunderbolt temperature corrective function may not be adequate for other oscillators specially when externally connected. Can this function not be disabled? I believe the end of the flagpole is not yet reached here. The LPRO (DATUM)and the EFRATOM/ Ball FRK, FRM and FRS models as well the FE5680A series unfortunately do contain only a VCXO inside and not an OCXO!. I found some more sources giving informations of interest: Disciplined Rb Standards are not (yet) in wide use, but they can already provide a short term stability down to better than 1E-11 according to http://tycho.usno.navy.mil/ptti/1989/Vol%2021_13.pdf PTS announce a stability with Allan Variance down to parts of E-13 (GPS10RB). See GPS10R/RB - 10 MHz GPS Disciplined Rubidium Frequency Standards http://www.ptsyst.com/GPS10RB-B.pdf and Why Rubidium Outperforms OXCO based units http://www.ptsyst.com/AppNote2.pdf Using a carrier phase tracking GPS Receiver, special techniques and algorythms, Quartzlock in UK even claim to have achieved a short-term stability down to E-13 and E-14 as long term accuracy. GPS Synchronized Disciplined Rubidium Frequency Standard from TRAK Systems http://tycho.usno.navy.mil/ptti/1998/Vol%2030_20.pdf http://www.quartzlock.com/products.asp?product=69 Concerning the lifetime of RbOs: According SRS the PRS10 lamp life is 20 years, the manual of LPRO says: The LPRO is designed for long operating periods without maintenance (MTBF 32h below and @ 30°C amb.) including a long life Rb lamp with a goal to exceed 10 years, which will not necessarily be the end of life. Information from Datum: Over our 27 years of Rubidium oscillator development and production experience, we have shown that the lifetime of our physics package is virtually unlimited. Datum is the only company worldwide, being able to guarantee a lifetime warranty on lamp and cell. There are no “wear-out” or “use-up” mechanisms in a Datum Efratom Rubidium oscillator. (http://www.amtestpl.com/DATUM/GmbH/Rubidium-Note-e.pdf) So I don't see a big problem with RbO's lifetime. regards Arnold ___ 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] Housing LPRO and Thunderbolt together
Chis and Charles - Thanks for the links - those were the ones I was looking for... Brent On Fri, Apr 22, 2011 at 9:03 PM, Chris Albertson albertson.ch...@gmail.com wrote: On Fri, Apr 22, 2011 at 5:42 PM, brent evers brent.ev...@gmail.com wrote: ... If anyone has a decent source for 1U chassis that I could mount a pair of tbolts in, I would appreciate it. These were generic 1U rackmount chassis - not 'server' chassis with a bunch of preplanned holes. Small shop, decent prices http://www.par-metal.com/product-rmc-10series.php -- = 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] Housing LPRO and Thunderbolt together
On 04/22/2011 11:37 PM, WB6BNQ wrote: Hi Pete, As Bob, K6RTM, pointed out the Thunderbolt and the Rubidium are two different animals all together. True, you can treat a Rubidium like it was a normal crystal oscillator, but it is not the same. The Rubidium has a definite life span, the more you run it the less the life. A high quality crystal oscillator, on the other hand, just gets better the longer you leave it on. Aside from nominal electrical component failures, the crystal blank in a properly designed circuit has no short term failure mechanism and will last for decades with constant applied power. The Rubidium’s life span is, at best, 10 years. The question is how long was it running before you got it ? I do not agree here. The main failure mechanism I've seen beyond normal electronic faults due to rubidium lamp, and it doesn't take much time effort and skills to solve that particular issue. It's not a wear mechanism as such, more a unfortunate displacement issue, which can be sufficiently reversed. It is a problem inherent to a popular lamp design, which is not to say it is true for all rubidium lamps either... As for your project boxes, I would use the rack mounted box to house the Thunderbolt, distribution amps and perhaps a couple of other oscillators (like the hp 10811) along with quality power sources. Because crystal oscillators like a constant operating condition, do consider battery power for the lab to handle those occasional mains power drops. I would use the portable box for the Rubidium oscillator and include a battery option depending upon your intent. The emphasis should be to have very quiet and stable power supplies for both projects. Even batteries have a fair amount of noise so make the mains power (and battery) voltage high enough to allow for running a quality regulation circuit. Recall that Rubidiums also like stable temperature. Possibly a controlled fan could be used to control the temperature of the rubidium. Passive radiation through heat-sink isn't the best solution. Raising the temperature of the cooling surface but keeping a tighter control of its temperature lowers the need to consume power by the heaters and will lower the current through transistors... 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] Housing LPRO and Thunderbolt together
Magnus, I just cannot believe you are disagreeing with me ! However, I still stand behind my statement. Considering the two mechanisms, the quartz blank seldom fail in a proper design. Whereas the Rubidium is guaranteed to fail as you have admitted. But you do have a point that the Rubidium can be revived with a good degree of success. The quartz blank, if fractured, is no more period. And of course we are ignoring all the standard electronic parts, etc., and only talking about the primary mechanisms. 73BillWB6BNQ Magnus Danielson wrote: I do not agree here. The main failure mechanism I've seen beyond normal electronic faults due to rubidium lamp, and it doesn't take much time effort and skills to solve that particular issue. It's not a wear mechanism as such, more a unfortunate displacement issue, which can be sufficiently reversed. It is a problem inherent to a popular lamp design, which is not to say it is true for all rubidium lamps either... 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] Housing LPRO and Thunderbolt together
I have a dilemma and wish to access the collective wisdom of the group to advise a solution. I am building a clock generator based on a Thunderbolt. I have an LPRO and would also locate this in the same enclosure. I will also add a distribution amp and a divide chain in due course. The ultimate purpose of the set up is to provide a self contained clock generator set for my other test equipment, and also an experimental workstation for Rubidium and GPS disciplined experiments. Most of my other equipment is for 19-inch rack mounting. I have two potential solutions for housing the timing kit: 1. An old dismantled HP 4U scope chassis which will fit in with my other equipment physically, and can be racked if necessary. The PSU would have to be built into the same enclosure. 2. A pair of Anritsu instrument cases which once house a bit error test set. The two units clip together beautifully, and are free standing. As there are two units, this solution would allow me to build the PSUs in one case and the more sensitive timing electronics in the other. These units cannot be racked on account of their form factors. Both solutions will require me to do some bespoke metalwork, but that is no problem for me and amounts to about the same amount of work for either solution. So what does the group advise? Is it vitally important to keep PSU components isolated from the timing electronics? I want to create the least noisy clock source given the components I have. Looking forward to hearing some opinions... Pete G4GJL ___ 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] Housing LPRO and Thunderbolt together
My two cents, from living with both Thunderbolts and LPROs. They are entirely different kinds of beasts, and aren't suitable for long-term cohabitation without work. Tbolts like thermally stable environments, and are happier (meaning ADEV trending towards zero) when they are powered up in a stable environment for a long time (and with an antenna having a clear view of the sky). LPROs on the other hand, require a heatsink or thermal mass to dump heat and keep the baseplate at a safe operating temperature (if you're running one for more than ten or fifteen minutes at a time). The nature of the rubidium beast is also such that once it's locked, it's not going to vary a whole lot; I also don't tend to run a rubidium all the time, unlike the thunderbolts. I'm looking to package a LPRO in a portable-ish manner with a backup battery good for an hour or so of operation. The idea is to check/trim it with a (non-portable) Thunderbolt and then carry it to where it's needed. Are you proposing to use the rubidium to provide a reference until the tbolt acquires lock? 73 bob k6rtm -- Message: 2 Date: Fri, 22 Apr 2011 16:48:07 +0100 (BST) From: g4...@btopenworld.com To: time-nuts@febo.com Subject: [time-nuts] Housing LPRO and Thunderbolt together Message-ID: 425854.57579...@web86602.mail.ird.yahoo.com Content-Type: text/plain; charset=utf-8 I have a dilemma and wish to access the collective wisdom of the group to advise a solution. I am building a clock generator based on a Thunderbolt. I have an LPRO and would also locate this in the same enclosure. I will also add a distribution amp and a divide chain in due course. The ultimate purpose of the set up is to provide a self contained clock generator set for my other test equipment, and also an experimental workstation for Rubidium and GPS disciplined experiments. ___ 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] Housing LPRO and Thunderbolt together
Having over years looked down at Thunderbolt using GPS/Shera/Rb's and Cesium Standards I finally broke down and bought a Tbolt when there where some available for a day for $75. Decided at that price I can not go wrong. Now my counters, Spectrum Analyzer and all Sig. Generators are fed by the Tbolt. I even use the 1PPS in some applications as a GPS replacement. There have been recent discussions of using a fan to keep constant temperature, something I highly recommend. Make it a stand alone unit with 1 PPS and 10MHz distribution front and back. With out kilo buck investment this will be the best. 14 NMH AA cells will make a nice simple backup unless you want to use switchers combined with linear regulators. Now you can play with the LPRO, again I would use a small fan. Bert Kehren In a message dated 4/22/2011 11:48:27 A.M. Eastern Daylight Time, g4...@btopenworld.com writes: I have a dilemma and wish to access the collective wisdom of the group to advise a solution. I am building a clock generator based on a Thunderbolt. I have an LPRO and would also locate this in the same enclosure. I will also add a distribution amp and a divide chain in due course. The ultimate purpose of the set up is to provide a self contained clock generator set for my other test equipment, and also an experimental workstation for Rubidium and GPS disciplined experiments. Most of my other equipment is for 19-inch rack mounting. I have two potential solutions for housing the timing kit: 1. An old dismantled HP 4U scope chassis which will fit in with my other equipment physically, and can be racked if necessary. The PSU would have to be built into the same enclosure. 2. A pair of Anritsu instrument cases which once house a bit error test set. The two units clip together beautifully, and are free standing. As there are two units, this solution would allow me to build the PSUs in one case and the more sensitive timing electronics in the other. These units cannot be racked on account of their form factors. Both solutions will require me to do some bespoke metalwork, but that is no problem for me and amounts to about the same amount of work for either solution. So what does the group advise? Is it vitally important to keep PSU components isolated from the timing electronics? I want to create the least noisy clock source given the components I have. Looking forward to hearing some opinions... Pete G4GJL ___ 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] Housing LPRO and Thunderbolt together
Hi Pete, As Bob, K6RTM, pointed out the Thunderbolt and the Rubidium are two different animals all together. True, you can treat a Rubidium like it was a normal crystal oscillator, but it is not the same. The Rubidium has a definite life span, the more you run it the less the life. A high quality crystal oscillator, on the other hand, just gets better the longer you leave it on. Aside from nominal electrical component failures, the crystal blank in a properly designed circuit has no short term failure mechanism and will last for decades with constant applied power. The Rubidiums life span is, at best, 10 years. The question is how long was it running before you got it ? A high quality crystal oscillator has excellent short term specs but does have drift and aging functions that severely limit its use for long term purposes. Long term meaning more than a few hours for the best. That is where the Rubidium oscillator takes over as its drift function is measured in days to a month or more. For high quality measurements, the crystal excels for measurement times of less than 10 seconds, as the Rubidium is noisier in that time frame. That is, for taking readings on a one second to second basis, such as with a high resolution time interval counter, the crystal excels. However, if the period of the measurement is longer, then the Rubidium would be a better choice. For portable purposes the Rubidium also excels as its retrace is much better than a crystal oscillator. You also do not need to wait the thirty to sixty days for the crystal to stabilize. The Rubidium will be very close to its original set point in about 20 minutes. Adding GPS to mix has its own issues. First, you need to know the coordinates precisely or spend a couple of days getting a damn good fix. The GPS is quite noisy in the short term and the oscillator that is steered by the GPS has that noise show up in its output. That is mitigated by having a high quality crystal oscillator where the GPS control loop seldom makes corrections; perhaps once an hour or more. That is how the Thunderbolt works and depending upon its internal crystal oscillator, it may possibly be tweaked to perform better then the standard factory settings. As for use, it all depends upon what and how youre making measurements. With a nominal 8 or 9 digit counter, for example, you may not notice all of the above issues because they are typically beyond the resolution of the equipment in most cases. In other measurement processes it may be of major concern. As for your project boxes, I would use the rack mounted box to house the Thunderbolt, distribution amps and perhaps a couple of other oscillators (like the hp 10811) along with quality power sources. Because crystal oscillators like a constant operating condition, do consider battery power for the lab to handle those occasional mains power drops. I would use the portable box for the Rubidium oscillator and include a battery option depending upon your intent. The emphasis should be to have very quiet and stable power supplies for both projects. Even batteries have a fair amount of noise so make the mains power (and battery) voltage high enough to allow for running a quality regulation circuit. My two cents ! 73BillWB6BNQ g4...@btopenworld.com wrote: I have a dilemma and wish to access the collective wisdom of the group to advise a solution. I am building a clock generator based on a Thunderbolt. I have an LPRO and would also locate this in the same enclosure. I will also add a distribution amp and a divide chain in due course. The ultimate purpose of the set up is to provide a self contained clock generator set for my other test equipment, and also an experimental workstation for Rubidium and GPS disciplined experiments. Most of my other equipment is for 19-inch rack mounting. I have two potential solutions for housing the timing kit: 1. An old dismantled HP 4U scope chassis which will fit in with my other equipment physically, and can be racked if necessary. The PSU would have to be built into the same enclosure. 2. A pair of Anritsu instrument cases which once house a bit error test set. The two units clip together beautifully, and are free standing. As there are two units, this solution would allow me to build the PSUs in one case and the more sensitive timing electronics in the other. These units cannot be racked on account of their form factors. Both solutions will require me to do some bespoke metalwork, but that is no problem for me and amounts to about the same amount of work for either solution. So what does the group advise? Is it vitally important to keep PSU components isolated from the timing electronics? I want to create the least noisy clock source given the components I have. Looking forward to hearing some opinions... Pete G4GJL ___ time-nuts mailing list --
Re: [time-nuts] Housing LPRO and Thunderbolt together
Somewhat related to this, someone posted a link for 1U chassis a while back. I thought I saved the link, but can't find it, and since the text of posts can't be searched from the archives, can't find mention of it that way either. If anyone has a decent source for 1U chassis that I could mount a pair of tbolts in, I would appreciate it. These were generic 1U rackmount chassis - not 'server' chassis with a bunch of preplanned holes. Brent On Fri, Apr 22, 2011 at 5:37 PM, WB6BNQ wb6...@cox.net wrote: Hi Pete, As Bob, K6RTM, pointed out the Thunderbolt and the Rubidium are two different animals all together. True, you can treat a Rubidium like it was a normal crystal oscillator, but it is not the same. The Rubidium has a definite life span, the more you run it the less the life. A high quality crystal oscillator, on the other hand, just gets better the longer you leave it on. Aside from nominal electrical component failures, the crystal blank in a properly designed circuit has no short term failure mechanism and will last for decades with constant applied power. The Rubidium’s life span is, at best, 10 years. The question is how long was it running before you got it ? A high quality crystal oscillator has excellent short term specs but does have drift and aging functions that severely limit its use for long term purposes. Long term meaning more than a few hours for the best. That is where the Rubidium oscillator takes over as its drift function is measured in days to a month or more. For high quality measurements, the crystal excels for measurement times of less than 10 seconds, as the Rubidium is noisier in that time frame. That is, for taking readings on a one second to second basis, such as with a high resolution time interval counter, the crystal excels. However, if the period of the measurement is longer, then the Rubidium would be a better choice. For portable purposes the Rubidium also excels as its retrace is much better than a crystal oscillator. You also do not need to wait the thirty to sixty days for the crystal to stabilize. The Rubidium will be very close to its original set point in about 20 minutes. Adding GPS to mix has its own issues. First, you need to know the coordinates precisely or spend a couple of days getting a damn good fix. The GPS is quite noisy in the short term and the oscillator that is steered by the GPS has that noise show up in its output. That is mitigated by having a high quality crystal oscillator where the GPS control loop seldom makes corrections; perhaps once an hour or more. That is how the Thunderbolt works and depending upon its internal crystal oscillator, it may possibly be tweaked to perform better then the standard factory settings. As for use, it all depends upon what and how you’re making measurements. With a nominal 8 or 9 digit counter, for example, you may not notice all of the above issues because they are typically beyond the resolution of the equipment in most cases. In other measurement processes it may be of major concern. As for your project boxes, I would use the rack mounted box to house the Thunderbolt, distribution amps and perhaps a couple of other oscillators (like the hp 10811) along with quality power sources. Because crystal oscillators like a constant operating condition, do consider battery power for the lab to handle those occasional mains power drops. I would use the portable box for the Rubidium oscillator and include a battery option depending upon your intent. The emphasis should be to have very quiet and stable power supplies for both projects. Even batteries have a fair amount of noise so make the mains power (and battery) voltage high enough to allow for running a quality regulation circuit. My two cents ! 73BillWB6BNQ g4...@btopenworld.com wrote: I have a dilemma and wish to access the collective wisdom of the group to advise a solution. I am building a clock generator based on a Thunderbolt. I have an LPRO and would also locate this in the same enclosure. I will also add a distribution amp and a divide chain in due course. The ultimate purpose of the set up is to provide a self contained clock generator set for my other test equipment, and also an experimental workstation for Rubidium and GPS disciplined experiments. Most of my other equipment is for 19-inch rack mounting. I have two potential solutions for housing the timing kit: 1. An old dismantled HP 4U scope chassis which will fit in with my other equipment physically, and can be racked if necessary. The PSU would have to be built into the same enclosure. 2. A pair of Anritsu instrument cases which once house a bit error test set. The two units clip together beautifully, and are free standing. As there are two units, this solution would allow me to build the PSUs in one case and the more
Re: [time-nuts] Housing LPRO and Thunderbolt together
On Fri, Apr 22, 2011 at 5:42 PM, brent evers brent.ev...@gmail.com wrote: ... If anyone has a decent source for 1U chassis that I could mount a pair of tbolts in, I would appreciate it. These were generic 1U rackmount chassis - not 'server' chassis with a bunch of preplanned holes. Small shop, decent prices http://www.par-metal.com/product-rmc-10series.php -- = 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] Housing LPRO and Thunderbolt together
and since the text of posts can't be searched from the archives Google works. Go to the advanced search page and put *.febo.com into the box labeled Search within a site or domain:, or add site:*.febo.com to the main search box. -- 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.
