Re: [time-nuts] time-nuts Digest, Vol 121, Issue 65
On Sat, 23 Aug 2014 16:51:06 -0500, Dave M wrote: Thanks for that suggestion, Ed. After a bit of reading in the X72 Reference Guide, it appears that the X72 does have a 1PPS input. That would be considerably easier than trying to interface the Rb into the GPSDO. Still trying to understand what the manual is telling me. Next thing is to determine if my unit has that option enabled (firmware option). That will be a chore for after the holiday... really busy next week. My X72 has firmware 4.xx , and does not support 1PPS. I seem to remember you need v 5.xx I'm quite sure i got it from here (*bay# 180791401271) , and after i complained about the missing 1PPS and told seller the fw. version i had in mine, he wrote the fw. version info on the page. /CFO Denmark ___ 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] time-nuts Digest, Vol 121, Issue 65
Hal there is not one straight answer, as mentioned before these units are intended for commercial applications with large temperature ranges. Most have added frequency compensation using heater current sensing for C field adjustment or in the case of the FE 5680A DDS control. Looking close at the 5680 you can expect 4 E-11 per 1 C. Bert Kehren In a message dated 8/23/2014 9:42:15 P.M. Eastern Daylight Time, hmur...@megapathdsl.net writes: kb...@n1k.org said: If you have a temperature stable environment (or create one) you can get some very good results with an (good) Rb locked to a (good) GPS via a proper long time constant setup. It’s not easy, but it can be done. What's the temperature sensitivity of the typical telco-surplus Rb unit? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] time-nuts Digest, Vol 121, Issue 65
Hi The typical small Rb’s are temperature compensated. They have a real tempco of a bit less than a ppb. It gets corrected to about 10X better than that using data from an internal temp sensor. Correction is often three point, so it may or may not track the actual performance of the unit at all temperatures. There are a couple of gotcha’s with this approach. The first is that the sensor needs to track what’s going on with the unit. If you do things that change the thermals (heat flow) of the unit, that may no longer be true. The next issue is the step size of the correction. It’s digital, if you vary back and forth barely over a step boundary, it will quite happily modulate your Rb. The net result will be a unit with worst ADEV than one with the correction disabled. This is very much a “your MPG may vary” sort of thing. If you happen to have a golden unit that is very flat before correction, the correction will not impact you much. If you have one with a third order curve to it’s pre-correction characteristic, the three point / two line segment correction isn’t gong be as effective as it might be. Also o the list of things to be aware of: Rb’s tune with a magnetic field. Changing the local field can change the output frequency. Rb’s have a sensitivity to barometric pressure. Eliminating this is a bit hard. Correcting for it may be the better approach. Again both of these effects vary unit to unit. Your part may not be as sensitive as my part. Lots of fun. Bob On Aug 23, 2014, at 9:41 PM, Hal Murray hmur...@megapathdsl.net wrote: kb...@n1k.org said: If you have a temperature stable environment (or create one) you can get some very good results with an (good) Rb locked to a (good) GPS via a proper long time constant setup. It’s not easy, but it can be done. What's the temperature sensitivity of the typical telco-surplus Rb unit? -- These are my opinions. I hate spam. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] EFC info on Trimble 34310-T OXCO
Charles I agree with every thing you wrote and I am implementing many of your recommendations. Forty years ago I bought a 15 foot Alu channel to make small frequency counter housings, always small, and at the time I did have access to a machine shop so I made end plates. Still have five foot pieces now I cut then off in 1 lb pieces and use them for tbolt, FE 405 B, FE 5650 and even a HP 10811 taken out of the can. As I said before am waiting for the small spheres and will see what happens. Working on a GPSDO for the FE 5680A and the FE 405 B I did find out the hard way what moving air will do. When AC season started my 405 tests showed the AC cycling it has a digital tuning resolution of 5.7 E-15.. The nicely assembled packaged unit ended up in an other RS chassis with bubble pack on each end reduced AC influence but you can still see it. If you like to see some data contact me off list file is to large to post. Picture of my Alu channel is attached. Bert Kehren In a message dated 8/23/2014 10:20:19 P.M. Eastern Daylight Time, csteinm...@yandex.com writes: Ed wrote: I agree with your statement regarding the determination of the optimum time constant, but, as Bob Camp mentioned, temperature change has a significant impact on setting the value. My 'lab' is a non-airconditioned bedroom. My Tbolt doesn't have any active temperature control. If I set the time constant to the point that Lady Heather thinks is optimum, I see large swings in PPS offset when I open the window and the temperature changes by a few degrees C. If I leave the time constant at the default of 100 seconds, the swimgs are drastically reduced. Active temperature control is on my 'round tuit' list. Bert wrote: As to Ed's and Bob's comments our projects are not able to compete with commercial products and I do not think that should be our goals. Having spend extensive time on temperature control, I limit my self to 10 C and use fans on all Rb's and passive on OCXO's. Concern about vibration induced noise on the OCXO made me remove the fan on the tbolt. Added a lot of mass and now ordered some foam balls from China to fill the enclosure as some one recommended. Well, yeah, it goes without saying (or at least I thought it would) that one must keep the rate of change of temperature of the OCXO low enough that its oven can keep the crystal temperature within design bounds at all times. I just assume that any time nut would do this, since it is extremely simple and costs next to nothing (look in the archives for my previous posts about metal boxes, metal enclosures, and thermal capacitance in connection with OCXOs). Active temperature control is NOT necessary. Which is not to say it's a bad idea, it's just not necessary to stabilize any OCXO worth owning by a time nut. (I'm not sure the MV-89 qualifies, even if you are lucky enough to get a good one. There has been some discussion on this list about the temperature control loop being quasi-stable and tending to oscillate or even latch under some conditions.) I also see no reason why amateur efforts cannot surpass the performance of commercial products, particularly if we assume that the environmental conditions are limited to those encountered in living space, not a radio shelter exposed to the elements at a remote tower. That is why I've been critical of designs that aim only to do the best that can be done for $5, or the best that can be done with a small ARM and 3 transistors. Given good design, there is no reason why an inexpensive DIY GPSDO shouldn't handily outperform a Thunderbolt (using the same OCXO), with two conditions: (i) environmental conditions are limited to those encountered in living space, and (ii) performance during holdover is neglected. The reasons why most DIY designs do not work as well as commercial designs, even if they use OCXOs of equal quality, is that their designers evidently cannot design ADPLLs of sufficient performance to do justice to the OCXO. (This includes implementing whatever means of phase comparison and sampling are chosen, the DSP loop filter, sawtooth correction, and the NCO or DAC/EFC design.) Doing all of this right isn't particularly expensive, it just takes a designer who has the skills and is willing to devote the effort. As a mentor once told me, Good thinking isn't any more expensive than bad thinking. Some of the performance gain would be in reducing the rate of temperature change seen by the OCXO, either passively as I have advocated and described before, or actively. The other main improvement would be setting the PLL crossover out where it belongs, which becomes possible when the rate of change of temperature is controlled. Avoiding a few common mistakes would provide some additional performance gains. While the foam peanuts, which I mentioned in a previous post, are helpful in
Re: [time-nuts] EFC info on Trimble 34310-T OXCO
Hi Dave, On 8/23/2014 3:51 PM, Dave M wrote: Thanks for that suggestion, Ed. After a bit of reading in the X72 Reference Guide, it appears that the X72 does have a 1PPS input. That would be considerably easier than trying to interface the Rb into the GPSDO. Still trying to understand what the manual is telling me. Next thing is to determine if my unit has that option enabled (firmware option). That will be a chore for after the holiday... really busy next week. What would that (1PPS disciplining) do for me... in terms of maintaining the Rb frequency accurately set? Would it be as accurate as having the Rb disciplined via the EFC input? It's kind of overkill, but by connecting the 1 PPS from the NTBW50AA to the X72, the X72 will be disciplined to the 1 PPS so the frequency will be accurate. The question is how well will it be disciplined, i.e. what will the Allen Deviation graph look like. I have a few X72 and SA-22c (X72's cousin), but none of them have that option. I don't know of any published data on it. Maybe you can tell us how well it performs. In general, I just don't see the point of disciplining a Rb standard to GPS. I don't understand what will be gained by doing it. I have a Z3801A and a Tbolt plus a free-running FRK as a house standard. I occasionally compare the FRK to the Z3801A but the drift is so low (~1e-12 per month over 9 months) that I see no reason to link them. One exception that I recently discussed on another forum was a guy who lives in a ground floor, north-facing condo. He might need to have a disciplined Rb standard due to poor GPS visibility. Ed Sorry for forgetting to change the Subject line on my last post. I see the futility of trying to integrate a Rb oscillator into a GPS receiver. As it turns out, my X72 doesn't have the 1PPS input option enabled, so that's a moot point. end result: I now have a couple of GPSDOs and a Rb that I can use separately, as needed. I would like to have a frequency comparator that can handle 10 MHz inputs natively without having to divide them down to 5 MHz. I have a Fluke/Montronics model 103A Frequency Comparator, but its max frequency input is 5MHz. I have a TADD-2 divider board, but I want to build a two-channel divider board to dedicate to the Fluke comparator. Which logic family is most suitable for such use; ALS, AC, etc.? Low jitter would be the critical parameter? I only need to divide by and 10, and maybe 100. My original dream, and the impetus for this thread, was to have a frequency standard having the excellent short-term stability of the Rb, but have it disciplined to the GPS to maintain its long-term accuracy without having to correct the Rb manually. My conclusion; it's now quite obvious that the old-school manual method is probably easiest and best. I'll set the frequency on the Rb, watch its performance for a few months, and use it as the main frequency source for my bench. Thanks for all the advice. Dave M ___ 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] Effect of sampling intervals on ADEV measurements
I compared an Austron 1250A to an FTS 1050A, both 5 MHz quartz frequency standards. I beat both against a 5Hz offset using a Riley DMTD device to provide a 1e6 time resolution increase. There was about a 1.15e-10 frequency difference between the two oscillators (two weeks on, it's about 5.6s-11) The two oscillators measure about 6e-13 ADEV from 8 to 100 seconds, assuming the phase difference at the the ZCDs is between .2 and .11 s. When the time interval, as measured by the counter, drops below .11s two distinct slopes become apparent on the Timelab Original Phase Window; one from .2s to .11s and the other from .11s to 0s. As the phase wraps the cycle repeats. I have thought about this a fair bit and the only thing that makes much sense is that with small phase differences I get 5 samples per second but as the phase difference lengthens, the TIC can no longer deliver 5 sps. It has to drop to 2.5 samples per second. If I'm not mistaken, I also see a similar, but less pronounced effect using PicTicII's as shown in Riley's article. TimeLab sets the sampling time based on monitoring the initial input from the TIC and I assume a change in sampling rate will affect the slope. Does this make any sense or I am I barking up the wrong tree here? Anyone using time tagging instead of TICs? Any serious pitfalls there? Thanks, Bob Darby ___ 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] time-nuts Digest, Vol 121, Issue 65
Hi Bob: I think that's what's done in the SRS PRS10 http://www.prc68.com/I/PRS10.shtml Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Bob Camp wrote: Hi If you lock an Rb to GPS, you need / want / should do it with a *very* long time constant. Numbers in the one day to several days range are commonly seen. If you lock it up with a tighter (shorter time constant) loop, it will just wander around as it follows the GPS input. That’s what would happen if you hook your Rb to your Trimble and turn on the disciplining on the Rb. It will significantly degrade the stability of the Rb. If you have a temperature stable environment (or create one) you can get some very good results with an (good) Rb locked to a (good) GPS via a proper long time constant setup. It’s not easy, but it can be done. Bob On Aug 23, 2014, at 6:31 PM, Ed Palmer ed_pal...@sasktel.net wrote: Hi Dave, On 8/23/2014 3:51 PM, Dave M wrote: Thanks for that suggestion, Ed. After a bit of reading in the X72 Reference Guide, it appears that the X72 does have a 1PPS input. That would be considerably easier than trying to interface the Rb into the GPSDO. Still trying to understand what the manual is telling me. Next thing is to determine if my unit has that option enabled (firmware option). That will be a chore for after the holiday... really busy next week. What would that (1PPS disciplining) do for me... in terms of maintaining the Rb frequency accurately set? Would it be as accurate as having the Rb disciplined via the EFC input? It's kind of overkill, but by connecting the 1 PPS from the NTBW50AA to the X72, the X72 will be disciplined to the 1 PPS so the frequency will be accurate. The question is how well will it be disciplined, i.e. what will the Allen Deviation graph look like. I have a few X72 and SA-22c (X72's cousin), but none of them have that option. I don't know of any published data on it. Maybe you can tell us how well it performs. In general, I just don't see the point of disciplining a Rb standard to GPS. I don't understand what will be gained by doing it. I have a Z3801A and a Tbolt plus a free-running FRK as a house standard. I occasionally compare the FRK to the Z3801A but the drift is so low (~1e-12 per month over 9 months) that I see no reason to link them. One exception that I recently discussed on another forum was a guy who lives in a ground floor, north-facing condo. He might need to have a disciplined Rb standard due to poor GPS visibility. Ed Thanks, Dave M Message: 5 Date: Fri, 22 Aug 2014 16:19:45 -0600 From: Ed Palmer ed_pal...@sasktel.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] EFC info on Trimble 34310-T OXCO Message-ID: 53f7c201.5070...@sasktel.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed Have you checked your X72 to see if it has the 1 PPS discipline option? That would be a lot easier (and probably better) than your proposed transplant. Ed On 8/22/2014 12:39 PM, Dave M wrote: Does anyone have any info on the OXCO in the Nortel/Trimble NTBW50AA-17 GPSTM receiver? The OXCO is labeled as Trimble 34310-T. I see some Trimble 34310-T oscillators on Ebay with pinouts labeled, but no other info. Specifically, I'd like to know the EFC characteristics for it. I'm thinking of the possibility of pulling the OXCO out of the GPSTM and subbing in a 10 MHz Rubidium, and using the GPSTM to discipline the Rubidium. My Rubidium is a Symmetricom X72, recently purchased. It seems to be working well. Does anyone know the differences between the three OXCOs used in the GPSTM receivers (T, T2 and Oak)? Thanks for some insight, Dave M ___ 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] time-nuts Digest, Vol 121, Issue 65
Hi It is not what is done in the Efratom Rb’s. Their pps input is set up to get things on frequency / on time quickly. The assumption is that you plug it into a pps to get it “right” and then take off on your mission. That takes them into the short (for a Rb) time constant region. Bob On Aug 24, 2014, at 5:56 PM, Brooke Clarke bro...@pacific.net wrote: Hi Bob: I think that's what's done in the SRS PRS10 http://www.prc68.com/I/PRS10.shtml Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Bob Camp wrote: Hi If you lock an Rb to GPS, you need / want / should do it with a *very* long time constant. Numbers in the one day to several days range are commonly seen. If you lock it up with a tighter (shorter time constant) loop, it will just wander around as it follows the GPS input. That’s what would happen if you hook your Rb to your Trimble and turn on the disciplining on the Rb. It will significantly degrade the stability of the Rb. If you have a temperature stable environment (or create one) you can get some very good results with an (good) Rb locked to a (good) GPS via a proper long time constant setup. It’s not easy, but it can be done. Bob On Aug 23, 2014, at 6:31 PM, Ed Palmer ed_pal...@sasktel.net wrote: Hi Dave, On 8/23/2014 3:51 PM, Dave M wrote: Thanks for that suggestion, Ed. After a bit of reading in the X72 Reference Guide, it appears that the X72 does have a 1PPS input. That would be considerably easier than trying to interface the Rb into the GPSDO. Still trying to understand what the manual is telling me. Next thing is to determine if my unit has that option enabled (firmware option). That will be a chore for after the holiday... really busy next week. What would that (1PPS disciplining) do for me... in terms of maintaining the Rb frequency accurately set? Would it be as accurate as having the Rb disciplined via the EFC input? It's kind of overkill, but by connecting the 1 PPS from the NTBW50AA to the X72, the X72 will be disciplined to the 1 PPS so the frequency will be accurate. The question is how well will it be disciplined, i.e. what will the Allen Deviation graph look like. I have a few X72 and SA-22c (X72's cousin), but none of them have that option. I don't know of any published data on it. Maybe you can tell us how well it performs. In general, I just don't see the point of disciplining a Rb standard to GPS. I don't understand what will be gained by doing it. I have a Z3801A and a Tbolt plus a free-running FRK as a house standard. I occasionally compare the FRK to the Z3801A but the drift is so low (~1e-12 per month over 9 months) that I see no reason to link them. One exception that I recently discussed on another forum was a guy who lives in a ground floor, north-facing condo. He might need to have a disciplined Rb standard due to poor GPS visibility. Ed Thanks, Dave M Message: 5 Date: Fri, 22 Aug 2014 16:19:45 -0600 From: Ed Palmer ed_pal...@sasktel.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] EFC info on Trimble 34310-T OXCO Message-ID: 53f7c201.5070...@sasktel.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed Have you checked your X72 to see if it has the 1 PPS discipline option? That would be a lot easier (and probably better) than your proposed transplant. Ed On 8/22/2014 12:39 PM, Dave M wrote: Does anyone have any info on the OXCO in the Nortel/Trimble NTBW50AA-17 GPSTM receiver? The OXCO is labeled as Trimble 34310-T. I see some Trimble 34310-T oscillators on Ebay with pinouts labeled, but no other info. Specifically, I'd like to know the EFC characteristics for it. I'm thinking of the possibility of pulling the OXCO out of the GPSTM and subbing in a 10 MHz Rubidium, and using the GPSTM to discipline the Rubidium. My Rubidium is a Symmetricom X72, recently purchased. It seems to be working well. Does anyone know the differences between the three OXCOs used in the GPSTM receivers (T, T2 and Oak)? Thanks for some insight, Dave M ___ 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
Re: [time-nuts] time-nuts Digest, Vol 121, Issue 65
Bob which Efratom are you talking about? Bert In a message dated 8/24/2014 6:33:12 P.M. Eastern Daylight Time, kb...@n1k.org writes: Hi It is not what is done in the Efratom Rb’s. Their pps input is set up to get things on frequency / on time quickly. The assumption is that you plug it into a pps to get it “right” and then take off on your mission. That takes them into the short (for a Rb) time constant region. Bob On Aug 24, 2014, at 5:56 PM, Brooke Clarke bro...@pacific.net wrote: Hi Bob: I think that's what's done in the SRS PRS10 http://www.prc68.com/I/PRS10.shtml Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Bob Camp wrote: Hi If you lock an Rb to GPS, you need / want / should do it with a *very* long time constant. Numbers in the one day to several days range are commonly seen. If you lock it up with a tighter (shorter time constant) loop, it will just wander around as it follows the GPS input. That’s what would happen if you hook your Rb to your Trimble and turn on the disciplining on the Rb. It will significantly degrade the stability of the Rb. If you have a temperature stable environment (or create one) you can get some very good results with an (good) Rb locked to a (good) GPS via a proper long time constant setup. It’s not easy, but it can be done. Bob On Aug 23, 2014, at 6:31 PM, Ed Palmer ed_pal...@sasktel.net wrote: Hi Dave, On 8/23/2014 3:51 PM, Dave M wrote: Thanks for that suggestion, Ed. After a bit of reading in the X72 Reference Guide, it appears that the X72 does have a 1PPS input. That would be considerably easier than trying to interface the Rb into the GPSDO. Still trying to understand what the manual is telling me. Next thing is to determine if my unit has that option enabled (firmware option). That will be a chore for after the holiday... really busy next week. What would that (1PPS disciplining) do for me... in terms of maintaining the Rb frequency accurately set? Would it be as accurate as having the Rb disciplined via the EFC input? It's kind of overkill, but by connecting the 1 PPS from the NTBW50AA to the X72, the X72 will be disciplined to the 1 PPS so the frequency will be accurate. The question is how well will it be disciplined, i.e. what will the Allen Deviation graph look like. I have a few X72 and SA-22c (X72's cousin), but none of them have that option. I don't know of any published data on it. Maybe you can tell us how well it performs. In general, I just don't see the point of disciplining a Rb standard to GPS. I don't understand what will be gained by doing it. I have a Z3801A and a Tbolt plus a free-running FRK as a house standard. I occasionally compare the FRK to the Z3801A but the drift is so low (~1e-12 per month over 9 months) that I see no reason to link them. One exception that I recently discussed on another forum was a guy who lives in a ground floor, north-facing condo. He might need to have a disciplined Rb standard due to poor GPS visibility. Ed Thanks, Dave M Message: 5 Date: Fri, 22 Aug 2014 16:19:45 -0600 From: Ed Palmer ed_pal...@sasktel.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] EFC info on Trimble 34310-T OXCO Message-ID: 53f7c201.5070...@sasktel.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed Have you checked your X72 to see if it has the 1 PPS discipline option? That would be a lot easier (and probably better) than your proposed transplant. Ed On 8/22/2014 12:39 PM, Dave M wrote: Does anyone have any info on the OXCO in the Nortel/Trimble NTBW50AA-17 GPSTM receiver? The OXCO is labeled as Trimble 34310-T. I see some Trimble 34310-T oscillators on Ebay with pinouts labeled, but no other info. Specifically, I'd like to know the EFC characteristics for it. I'm thinking of the possibility of pulling the OXCO out of the GPSTM and subbing in a 10 MHz Rubidium, and using the GPSTM to discipline the Rubidium. My Rubidium is a Symmetricom X72, recently purchased. It seems to be working well. Does anyone know the differences between the three OXCOs used in the GPSTM receivers (T, T2 and Oak)? Thanks for some insight, Dave M ___ 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
Re: [time-nuts] EFC info on Trimble 34310-T OXCO
Charles I use double bobble pack inside the Alu channel and I always start out by monitoring the OCXO and make sure it is at least 10 C below the spec range. The tbolt is center located and I use a combination of rubber mounts but suspended that they sell for hard drives and squares of double bubble pack. Vibration and thermal. Bert Kehren In a message dated 8/24/2014 8:26:02 P.M. Eastern Daylight Time, csteinm...@yandex.com writes: Bert wrote: As I said before am waiting for the small spheres and will see what happens. Monitor carefully, as I suspect the spheres will pack too tightly leaving too little airspace. You could easily burn down an OCXO if this proves to be the case and the oven control loop goes unstable. I'd put a thermal sensor on the OCXO itself for testing. Even if it doesn't burn down, you could find that the oven performance is degraded by (i) instability or quasi-instability of the oven controller, or (ii) too much thermal resistance (remember, you want to add as little thermal resistance as possible). On the other hand, mounting the OCXO as centrally as possible inside the outer enclosure on thermally non-conducting standoffs (teflon or nylon), with at least an inch of air on all six sides, has proven to work extremely well. When I described using packing peanuts (or similar) to break up the airflow, it was in the context of having already mounted the OCXO as centrally as possible inside the outer enclosure on thermally non-conducting standoffs with at least an inch of air on all six sides. And as I said, I have not found the additional step necessary once you have done this. It may even be counterproductive. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ 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] time-nuts Digest, Vol 121, Issue 65
Hi The Efratom that the original poster was referring to. All of the Efratom’s with PPS in pretty much work the same way. It’s one of those options you go crazy trying to find an example of and when you do it’s “ho hum, let’s look for something else”. Bob On Aug 24, 2014, at 8:19 PM, ewkeh...@aol.com wrote: Bob which Efratom are you talking about? Bert In a message dated 8/24/2014 6:33:12 P.M. Eastern Daylight Time, kb...@n1k.org writes: Hi It is not what is done in the Efratom Rb’s. Their pps input is set up to get things on frequency / on time quickly. The assumption is that you plug it into a pps to get it “right” and then take off on your mission. That takes them into the short (for a Rb) time constant region. Bob On Aug 24, 2014, at 5:56 PM, Brooke Clarke bro...@pacific.net wrote: Hi Bob: I think that's what's done in the SRS PRS10 http://www.prc68.com/I/PRS10.shtml Have Fun, Brooke Clarke http://www.PRC68.com http://www.end2partygovernment.com/2012Issues.html http://www.prc68.com/I/DietNutrition.html Bob Camp wrote: Hi If you lock an Rb to GPS, you need / want / should do it with a *very* long time constant. Numbers in the one day to several days range are commonly seen. If you lock it up with a tighter (shorter time constant) loop, it will just wander around as it follows the GPS input. That’s what would happen if you hook your Rb to your Trimble and turn on the disciplining on the Rb. It will significantly degrade the stability of the Rb. If you have a temperature stable environment (or create one) you can get some very good results with an (good) Rb locked to a (good) GPS via a proper long time constant setup. It’s not easy, but it can be done. Bob On Aug 23, 2014, at 6:31 PM, Ed Palmer ed_pal...@sasktel.net wrote: Hi Dave, On 8/23/2014 3:51 PM, Dave M wrote: Thanks for that suggestion, Ed. After a bit of reading in the X72 Reference Guide, it appears that the X72 does have a 1PPS input. That would be considerably easier than trying to interface the Rb into the GPSDO. Still trying to understand what the manual is telling me. Next thing is to determine if my unit has that option enabled (firmware option). That will be a chore for after the holiday... really busy next week. What would that (1PPS disciplining) do for me... in terms of maintaining the Rb frequency accurately set? Would it be as accurate as having the Rb disciplined via the EFC input? It's kind of overkill, but by connecting the 1 PPS from the NTBW50AA to the X72, the X72 will be disciplined to the 1 PPS so the frequency will be accurate. The question is how well will it be disciplined, i.e. what will the Allen Deviation graph look like. I have a few X72 and SA-22c (X72's cousin), but none of them have that option. I don't know of any published data on it. Maybe you can tell us how well it performs. In general, I just don't see the point of disciplining a Rb standard to GPS. I don't understand what will be gained by doing it. I have a Z3801A and a Tbolt plus a free-running FRK as a house standard. I occasionally compare the FRK to the Z3801A but the drift is so low (~1e-12 per month over 9 months) that I see no reason to link them. One exception that I recently discussed on another forum was a guy who lives in a ground floor, north-facing condo. He might need to have a disciplined Rb standard due to poor GPS visibility. Ed Thanks, Dave M Message: 5 Date: Fri, 22 Aug 2014 16:19:45 -0600 From: Ed Palmer ed_pal...@sasktel.net To: Discussion of precise time and frequency measurement time-nuts@febo.com Subject: Re: [time-nuts] EFC info on Trimble 34310-T OXCO Message-ID: 53f7c201.5070...@sasktel.net Content-Type: text/plain; charset=ISO-8859-1; format=flowed Have you checked your X72 to see if it has the 1 PPS discipline option? That would be a lot easier (and probably better) than your proposed transplant. Ed On 8/22/2014 12:39 PM, Dave M wrote: Does anyone have any info on the OXCO in the Nortel/Trimble NTBW50AA-17 GPSTM receiver? The OXCO is labeled as Trimble 34310-T. I see some Trimble 34310-T oscillators on Ebay with pinouts labeled, but no other info. Specifically, I'd like to know the EFC characteristics for it. I'm thinking of the possibility of pulling the OXCO out of the GPSTM and subbing in a 10 MHz Rubidium, and using the GPSTM to discipline the Rubidium. My Rubidium is a Symmetricom X72, recently purchased. It seems to be working well. Does anyone know the differences between the three OXCOs used in the GPSTM receivers (T, T2 and Oak)? Thanks for some insight, Dave M ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and
Re: [time-nuts] EFC info on Trimble 34310-T OXCO
Bert wrote: As I said before am waiting for the small spheres and will see what happens. Monitor carefully, as I suspect the spheres will pack too tightly leaving too little airspace. You could easily burn down an OCXO if this proves to be the case and the oven control loop goes unstable. I'd put a thermal sensor on the OCXO itself for testing. Even if it doesn't burn down, you could find that the oven performance is degraded by (i) instability or quasi-instability of the oven controller, or (ii) too much thermal resistance (remember, you want to add as little thermal resistance as possible). On the other hand, mounting the OCXO as centrally as possible inside the outer enclosure on thermally non-conducting standoffs (teflon or nylon), with at least an inch of air on all six sides, has proven to work extremely well. When I described using packing peanuts (or similar) to break up the airflow, it was in the context of having already mounted the OCXO as centrally as possible inside the outer enclosure on thermally non-conducting standoffs with at least an inch of air on all six sides. And as I said, I have not found the additional step necessary once you have done this. It may even be counterproductive. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
Re: [time-nuts] EFC info on Trimble 34310-T OXCO
Hi Keep in mind that the OCXO is likely (if it’s a modern part) optimized for TC at it’s normal thermal gain. The gain and set point are adjusted for a flat curve. If you bump either the gain or the set point you rotate the curve. Bob On Aug 24, 2014, at 8:36 PM, ewkeh...@aol.com wrote: Charles I use double bobble pack inside the Alu channel and I always start out by monitoring the OCXO and make sure it is at least 10 C below the spec range. The tbolt is center located and I use a combination of rubber mounts but suspended that they sell for hard drives and squares of double bubble pack. Vibration and thermal. Bert Kehren In a message dated 8/24/2014 8:26:02 P.M. Eastern Daylight Time, csteinm...@yandex.com writes: Bert wrote: As I said before am waiting for the small spheres and will see what happens. Monitor carefully, as I suspect the spheres will pack too tightly leaving too little airspace. You could easily burn down an OCXO if this proves to be the case and the oven control loop goes unstable. I'd put a thermal sensor on the OCXO itself for testing. Even if it doesn't burn down, you could find that the oven performance is degraded by (i) instability or quasi-instability of the oven controller, or (ii) too much thermal resistance (remember, you want to add as little thermal resistance as possible). On the other hand, mounting the OCXO as centrally as possible inside the outer enclosure on thermally non-conducting standoffs (teflon or nylon), with at least an inch of air on all six sides, has proven to work extremely well. When I described using packing peanuts (or similar) to break up the airflow, it was in the context of having already mounted the OCXO as centrally as possible inside the outer enclosure on thermally non-conducting standoffs with at least an inch of air on all six sides. And as I said, I have not found the additional step necessary once you have done this. It may even be counterproductive. Best regards, Charles ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there. ___ 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.
