Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia
On 6 February 2014 21:32, Jamieson (Jim) Rowe jimr...@optusnet.com.au wrote: So I decided to test this in a crude way, by inverting the FE-5680A and seeing what happened. And - lo and behold - it locked up within 2.5 minutes, and stayed locked until I turned off the power and let it go cold again. The next morning I applied power again, and within 3 minutes it locked up again with no problems. And it's been locked up now for over 48 hours... If you tilt it at some other angle other than 180 degrees, say 90, 135, 225 270 degrees, does it take the same time to lock up? I'm thinking if it is a magnetic effect, one might expect it to depend on the angle it is rotated. Dave ___ 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] How I got my FE-5680A to lock in Sydney, Australia
Hi Jim, This behaviour reinforces my thought that there's something physically wrong inside the unit. I'd be tapping it with the plastic handle of my screwdriver while I rotated it to see if it would lose lock. Think of it this way: Do you want to fix it now or have it fail again in a few months when you're using it for something important? Ed On 2/9/2014 6:39 PM, Jamieson (Jim) Rowe wrote: Hi again Magnus, Mark, Tom Harris, Ed Palmer et al, Well, before performing any surgery on my tricky little beasty, I decided to check its frequency swing limits when starting up in the 'inverted' position, and then when starting up in the right-side-up position. Here's what I found, as before looking at the frequency with my counter (GPSDXO 1pps timebase): Inverted position: swings between 9,999,798Hz and 10,000,001Hz, before locking. Normal position: swings between 9,999,756Hz and 10,000,057Hz, a few times. But wait for it -- it then locked up, reliably, in the right-side-up position! So now I'm really confused. It looks as if whatever was wrong with it before has somehow fixed itself, after running it for a couple of days locked in the inverted position... Anyway, I think I'll leave opening it up for a while (at least) -- since it's now running locked fine in the right-side-up position. I don't want to tempt fate, while its OK. What's that old adage? If it ain't broke, don't try to fix it. Cheers all, Jim Rowe -Original Message- From: Jamieson (Jim) Rowe Sent: Monday, February 10, 2014 8:05 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia Hi Magnus, Thanks for your further comments. As you probably saw in my reply to Mark Sims, I am proposing to check the swing limits 'before and after' inverting the unit, to check out the theory before I open it up and try tweaking C217. Cheers, Jim -Original Message- From: Magnus Danielson Sent: Sunday, February 09, 2014 7:34 PM To: time-nuts@febo.com Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia On 09/02/14 02:57, Jamieson (Jim) Rowe wrote: Hi Magnus, Thanks again for those further suggestions. I do have a GPSDO, and I had been able to use it with a counter to check that the FE-5680A was swinging either side of 10MHz. But I didn't make sure that it was swinging evenly each side of 10MHz . According to my notes it was swinging between 9.999770 and 10.36MHz -- i.e., about 230Hz low and about 36Hz high. But it was spending more of the time below 10MHz than above -- does this suggest to you that I should tweak C217 until it swings by about the same amount either way? Yes, that is exactly what I would do. 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] How I got my FE-5680A to lock in Sydney, Australia
On 10/02/14 16:59, Ed Palmer wrote: Hi Jim, This behaviour reinforces my thought that there's something physically wrong inside the unit. I'd be tapping it with the plastic handle of my screwdriver while I rotated it to see if it would lose lock. Think of it this way: Do you want to fix it now or have it fail again in a few months when you're using it for something important? I'm with Ed here. Keep working out the systematics of this beast, because you want to make sure it doesn't happen again. Also, it's now that you learn, you can then run it for 10 years without learning much more. 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] How I got my FE-5680A to lock in Sydney, Australia
Hi Bob, Charles, Dr David, Ed and Magnus, Thanks for those further helpful comments. OK, I will try seeing whether 'in between' orientations do make any difference, to provide further evidence regarding a possible magnetic effect. I'll also try the effect of tapping it with a plastic screwdriver handle. And if nothing more shows up, I'll try opening it up and looking for 'dry' or otherwise crook solder joints, etc. I did find the idea of rubidium movement inside the bulb an interesting one, though. It's a possibility, isn't it? Cheers, Jim Rowe -Original Message- From: Magnus Danielson Sent: Tuesday, February 11, 2014 8:40 AM To: time-nuts@febo.com Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia On 10/02/14 16:59, Ed Palmer wrote: Hi Jim, This behaviour reinforces my thought that there's something physically wrong inside the unit. I'd be tapping it with the plastic handle of my screwdriver while I rotated it to see if it would lose lock. Think of it this way: Do you want to fix it now or have it fail again in a few months when you're using it for something important? I'm with Ed here. Keep working out the systematics of this beast, because you want to make sure it doesn't happen again. Also, it's now that you learn, you can then run it for 10 years without learning much more. 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] How I got my FE-5680A to lock in Sydney, Australia
Hi Jim, I posted that mainly because there have been past threads about reviving Rb standards by heating the bulb, not because I have any evidence that that's the problem. Bob - AE6RV From: Jamieson (Jim) Rowe jimr...@optusnet.com.au To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Monday, February 10, 2014 4:57 PM Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia Hi Bob, Charles, Dr David, Ed and Magnus, Thanks for those further helpful comments. OK, I will try seeing whether 'in between' orientations do make any difference, to provide further evidence regarding a possible magnetic effect. I'll also try the effect of tapping it with a plastic screwdriver handle. And if nothing more shows up, I'll try opening it up and looking for 'dry' or otherwise crook solder joints, etc. I did find the idea of rubidium movement inside the bulb an interesting one, though. It's a possibility, isn't it? Cheers, Jim Rowe ___ 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] How I got my FE-5680A to lock in Sydney, Australia
Hi Charles, Sorry, but I didn't accidentally transpose the 'high' swing numbers. That's why I was so confused about the results. The counter I'm using is one that I designed myself. As an alternative to its internal 1MHz XCO timebase (with dividers down to 1Hz, 0.1Hz etc), it also allows you to use an external source of 1Hz pulses like those from a GPS receiver or a GPSDO, or a Rb Freq Reference. The dividers operate on these 1Hz/1pps pulses as well, to provide gating times of 1s, 10s, 100s or 1000s. It seems to work pretty well. Cheers, Jim Rowe -Original Message- From: Charles Steinmetz Sent: Monday, February 10, 2014 3:37 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia Jim wrote: Here's what I found, as before looking at the frequency with my counter (GPSDXO 1pps timebase): Inverted position: swings between 9,999,798Hz and 10,000,001Hz, before locking. Normal position: swings between 9,999,756Hz and 10,000,057Hz, a few times. Are you sure you didn't transpose the high swing numbers? As you state it above, the oscillator swings 203 Hz (peak-to-peak) when inverted and 301 Hz p-p right-side-up. If we swap the high swing numbers, it is 245 Hz inverted and 259 Hz right-side-up, which seems more plausible. There seems to be little reason why the absolute value of the sweep range would vary so much (203 to 301). Also, a normal range of 9,999,756 to 10,000,001 and an inverted range of 9,999,798 to 10,000,057 would seem to explain your previous results, while the results reported above would not. I'm a little confused by what you've said about your counter time base -- as I recall, you said you were feeding GPS 1pps to the counter. I'm not familiar with any counter that locks to 1pps -- most counters I'm familiar with lock to 10MHz (or in older gear, 5MHz or 1MHz). Can you say a bit more about your 1pps timebase? 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] How I got my FE-5680A to lock in Sydney, Australia
Jim wrote: Sorry, but I didn't accidentally transpose the 'high' swing numbers. That's why I was so confused about the results. No need to apologize, the facts are the facts! I take it that you recently received the GPS. If so, it is probably still settling into its new natural frequency after being off for a while and jostled around in shipping. It appears to have drifted far enough that it now scans through 10MHz in the normal position. At some point, you may find that it no longer locks in the inverted position because it has drifted too far to scan through 10MHz in that position (according to your figures, it was right on the edge when you took the data you posted). The counter I'm using is one that I designed myself. As an alternative to its internal 1MHz XCO timebase (with dividers down to 1Hz, 0.1Hz etc), it also allows you to use an external source of 1Hz pulses like those from a GPS receiver or a GPSDO, or a Rb Freq Reference. The dividers operate on these 1Hz/1pps pulses as well, to provide gating times of 1s, 10s, 100s or 1000s. It seems to work pretty well. For short gating times, I'd think that GPS PPS jitter might be a limitation. (That's the trick of a GPSDO -- the quartz [or rubidium] oscillator controls the short-term stability, at time intervals where it is better than the PPS, and the PPS controls the long-term stability at time intervals where it is better than the oscillator.) Specs for GPS engine PPS jitter seem to run from a low of around +/- 5nS to several times that, which would translate to a 1 second stability of 10^-8 to 10^-9 at best. A good quartz oscillator (or a well-designed GPSDO with a good quartz oscillator) should get you to 10^-11 or even into the neighborhood of 10^-12. You'll add a little jitter dividing by 10M, but it shouldn't be anywhere near as much as the 3-4 decades by which the quartz oscillator beats the PPS at 1S. 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] How I got my FE-5680A to lock in Sydney, Australia
On 09/02/14 02:57, Jamieson (Jim) Rowe wrote: Hi Magnus, Thanks again for those further suggestions. I do have a GPSDO, and I had been able to use it with a counter to check that the FE-5680A was swinging either side of 10MHz. But I didn't make sure that it was swinging evenly each side of 10MHz . According to my notes it was swinging between 9.999770 and 10.36MHz -- i.e., about 230Hz low and about 36Hz high. But it was spending more of the time below 10MHz than above -- does this suggest to you that I should tweak C217 until it swings by about the same amount either way? Yes, that is exactly what I would do. 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] How I got my FE-5680A to lock in Sydney, Australia
On 09/02/14 06:37, Mark Sims wrote: What was the timebase for your counter? I suspect that it is off freq and the Rb is not actually making it above 10 MHz. Inverting the Rb is causing a 2G shift in gravity to the Rb crystal probably shifting its freq enough to cause lock. This is what I have been thinking about, and adjusting the VCXO frequency should help. It would be interesting to confirm the 2G shift before adjustment. 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] How I got my FE-5680A to lock in Sydney, Australia
Hi Mark, I doubt if the counter is off frequency, since I'm using the 1pps pulses from my GPSDO as its timebase. So although there's a bit of short-term jitter, the longer-term count should be very close. I will try the experiment you suggest, though, and see what difference inversion makes to the frequency swing before locking (or non-locking). Thanks, -Original Message- From: Mark Sims Sent: Sunday, February 09, 2014 4:37 PM To: time-nuts@febo.com Subject: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia What was the timebase for your counter? I suspect that it is off freq and the Rb is not actually making it above 10 MHz. Inverting the Rb is causing a 2G shift in gravity to the Rb crystal probably shifting its freq enough to cause lock. ___ 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] How I got my FE-5680A to lock in Sydney, Australia
Hi Magnus, Thanks for your further comments. As you probably saw in my reply to Mark Sims, I am proposing to check the swing limits 'before and after' inverting the unit, to check out the theory before I open it up and try tweaking C217. Cheers, Jim -Original Message- From: Magnus Danielson Sent: Sunday, February 09, 2014 7:34 PM To: time-nuts@febo.com Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia On 09/02/14 02:57, Jamieson (Jim) Rowe wrote: Hi Magnus, Thanks again for those further suggestions. I do have a GPSDO, and I had been able to use it with a counter to check that the FE-5680A was swinging either side of 10MHz. But I didn't make sure that it was swinging evenly each side of 10MHz . According to my notes it was swinging between 9.999770 and 10.36MHz -- i.e., about 230Hz low and about 36Hz high. But it was spending more of the time below 10MHz than above -- does this suggest to you that I should tweak C217 until it swings by about the same amount either way? Yes, that is exactly what I would do. 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] How I got my FE-5680A to lock in Sydney, Australia
Hi again Magnus, Mark, Tom Harris, Ed Palmer et al, Well, before performing any surgery on my tricky little beasty, I decided to check its frequency swing limits when starting up in the 'inverted' position, and then when starting up in the right-side-up position. Here's what I found, as before looking at the frequency with my counter (GPSDXO 1pps timebase): Inverted position: swings between 9,999,798Hz and 10,000,001Hz, before locking. Normal position: swings between 9,999,756Hz and 10,000,057Hz, a few times. But wait for it -- it then locked up, reliably, in the right-side-up position! So now I'm really confused. It looks as if whatever was wrong with it before has somehow fixed itself, after running it for a couple of days locked in the inverted position... Anyway, I think I'll leave opening it up for a while (at least) -- since it's now running locked fine in the right-side-up position. I don't want to tempt fate, while its OK. What's that old adage? If it ain't broke, don't try to fix it. Cheers all, Jim Rowe -Original Message- From: Jamieson (Jim) Rowe Sent: Monday, February 10, 2014 8:05 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia Hi Magnus, Thanks for your further comments. As you probably saw in my reply to Mark Sims, I am proposing to check the swing limits 'before and after' inverting the unit, to check out the theory before I open it up and try tweaking C217. Cheers, Jim -Original Message- From: Magnus Danielson Sent: Sunday, February 09, 2014 7:34 PM To: time-nuts@febo.com Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia On 09/02/14 02:57, Jamieson (Jim) Rowe wrote: Hi Magnus, Thanks again for those further suggestions. I do have a GPSDO, and I had been able to use it with a counter to check that the FE-5680A was swinging either side of 10MHz. But I didn't make sure that it was swinging evenly each side of 10MHz . According to my notes it was swinging between 9.999770 and 10.36MHz -- i.e., about 230Hz low and about 36Hz high. But it was spending more of the time below 10MHz than above -- does this suggest to you that I should tweak C217 until it swings by about the same amount either way? Yes, that is exactly what I would do. 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. ___ 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] How I got my FE-5680A to lock in Sydney, Australia
Could this be a case of the Rb settling on the bottom of the bulb and then being vaporized when the bottom became the top? Bob From: Jamieson (Jim) Rowe jimr...@optusnet.com.au To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Sunday, February 9, 2014 6:39 PM Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia Hi again Magnus, Mark, Tom Harris, Ed Palmer et al, snip But wait for it -- it then locked up, reliably, in the right-side-up position! ___ 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] How I got my FE-5680A to lock in Sydney, Australia
Jim wrote: Here's what I found, as before looking at the frequency with my counter (GPSDXO 1pps timebase): Inverted position: swings between 9,999,798Hz and 10,000,001Hz, before locking. Normal position: swings between 9,999,756Hz and 10,000,057Hz, a few times. Are you sure you didn't transpose the high swing numbers? As you state it above, the oscillator swings 203 Hz (peak-to-peak) when inverted and 301 Hz p-p right-side-up. If we swap the high swing numbers, it is 245 Hz inverted and 259 Hz right-side-up, which seems more plausible. There seems to be little reason why the absolute value of the sweep range would vary so much (203 to 301). Also, a normal range of 9,999,756 to 10,000,001 and an inverted range of 9,999,798 to 10,000,057 would seem to explain your previous results, while the results reported above would not. I'm a little confused by what you've said about your counter time base -- as I recall, you said you were feeding GPS 1pps to the counter. I'm not familiar with any counter that locks to 1pps -- most counters I'm familiar with lock to 10MHz (or in older gear, 5MHz or 1MHz). Can you say a bit more about your 1pps timebase? 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] How I got my FE-5680A to lock in Sydney, Australia
On 07/02/14 20:40, beale wrote: The entry in the FE5680 FAQ on this subject may be helpful, if you haven't tried it already. http://ko4bb.com/dokuwiki/doku.php?id=precision_timing:fe5680a_faq#what_if_my_5680a_output_does_not_lock_up_after_several_minutes I have 3 of those units; one did not lock until I adjusted the trim-cap C217 to bring the free-running frequency of the oscillator into range. If you have a reasonably accurate counter you can check if this is the problem or not by seeing if the output frequency (which ramps up and down prior to lock) crosses through 10.00 MHz or not. Mine did not. This is why an oscillator trim is required. The oscillators offset is outside the lock-in range, DDS offset trim can possibly, for the DDS feedback version, cause lock-up, but the output won't be 10 MHz. This can naturally be used as a feature to have neat beat-frequencies in a DMTD setup, but otherwise not really recommended. Good that you have tried it and could point to the C217 trim-cap. Hopefully Jim can use that. Jim, do you have a GPSDO around? If so, use a counter and try to see what the top and bottom values in the sweeps are, adjust C217 so that the sweep range covers the 10 MHz line. Make sure you trim it with some margin to the edge of the sweep-range. Now, you should also be able to monitor how it locks up. 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] How I got my FE-5680A to lock in Sydney, Australia
Hi Jim, On 07/02/14 05:19, Jamieson (Jim) Rowe wrote: Hi Magnus, Thanks for those suggestions also. So if I understand you right, I'd be better off trying to tweak the oscillator tuning -- using the trimcap? Or did you mean via the RS-232C 'offset adjustment' command? I covered this in another message I just sent, but for completeness: You want the C217 trim-cap adjusted such that the lock-in sweep will sweep over 10 MHz, because that's where the synthesized magic locks up and you get 10 MHz out. If you use the offset adjustment, you could possibly get it to lock up, but not producing the 10 MHz you expect. Once you got the trick, it's actually quite fun to trim and get the warm fuzzy feeling of fixing it as it locks up. 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] How I got my FE-5680A to lock in Sydney, Australia
Hi Magnus, Thanks again for those further suggestions. I do have a GPSDO, and I had been able to use it with a counter to check that the FE-5680A was swinging either side of 10MHz. But I didn't make sure that it was swinging evenly each side of 10MHz . According to my notes it was swinging between 9.999770 and 10.36MHz -- i.e., about 230Hz low and about 36Hz high. But it was spending more of the time below 10MHz than above -- does this suggest to you that I should tweak C217 until it swings by about the same amount either way? Cheers, Jim -Original Message- From: Magnus Danielson Sent: Sunday, February 09, 2014 3:36 AM To: time-nuts@febo.com Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia Hi Jim, On 07/02/14 05:19, Jamieson (Jim) Rowe wrote: Hi Magnus, Thanks for those suggestions also. So if I understand you right, I'd be better off trying to tweak the oscillator tuning -- using the trimcap? Or did you mean via the RS-232C 'offset adjustment' command? I covered this in another message I just sent, but for completeness: You want the C217 trim-cap adjusted such that the lock-in sweep will sweep over 10 MHz, because that's where the synthesized magic locks up and you get 10 MHz out. If you use the offset adjustment, you could possibly get it to lock up, but not producing the 10 MHz you expect. Once you got the trick, it's actually quite fun to trim and get the warm fuzzy feeling of fixing it as it locks up. 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] How I got my FE-5680A to lock in Sydney, Australia
Hi Beale, Thanks for those suggestions. I had looked at that FAQ already, and when I checked the unit (before I inverted it) with a counter coupled to the 1pps signal from my GPSDO for its timebase, it was swinging through 10MHz (from -230Hz to +36Hz). But not evenly on either side, and it was spending somewhat longer below 10MHz than above. However I will try returning it to the 'right way up' position, then opening it up and running adjusting trim cap C217 to see if I can get it to swing equally either side of 10MHz. Hopefully I should then be able to get a reliable lock even 'right way up' -- right? Cheers, Jim Rowe -Original Message- From: beale Sent: Saturday, February 08, 2014 6:40 AM To: time-nuts@febo.com Subject: Re: [time-nuts]How I got my FE-5680A to lock in Sydney, Australia The entry in the FE5680 FAQ on this subject may be helpful, if you haven't tried it already. http://ko4bb.com/dokuwiki/doku.php?id=precision_timing:fe5680a_faq#what_if_my_5680a_output_does_not_lock_up_after_several_minutes I have 3 of those units; one did not lock until I adjusted the trim-cap C217 to bring the free-running frequency of the oscillator into range. If you have a reasonably accurate counter you can check if this is the problem or not by seeing if the output frequency (which ramps up and down prior to lock) crosses through 10.00 MHz or not. Mine did not. ___ 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] How I got my FE-5680A to lock in Sydney, Australia
Hi Ignacio, Thanks for your comments also. I will open up the unit and see if I can find any dry or poorly soldered joints, etc. Best regards, Jim Rowe -Original Message- From: EB4APL Sent: Saturday, February 08, 2014 12:21 AM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia Hi, I second the idea about a mechanical issue. When I opened my FRS-C I found that one of the connector pins had never been soldered, it only made mechanical contact with the PBC. Perhaps it showed an intermittent failure and was retired with low hours. Ignacio EB4APL On 07/02/2014 3:54, Ed Palmer wrote: Hi Jim, On 2/6/2014 3:32 PM, Jamieson (Jim) Rowe wrote: Hi again folks, You may (or may not) recall that a month or so ago, I asked for any information that might be available regarding how to fix a ‘used’ FE-5680A rubidium module from China (via ebay) which was tested by the supplier in China as working OK, but would not seem to lock up to rubidium here in Sydney. There wasn’t a great deal of info available, it seems, so I kept on checking ideas myself – mostly with no luck. The module would never lock, but kept cycling back and forth between about 9.999770MHz and 10.36MHz – ‘searching’ for a lock, but never finding it. Anyway, a couple of days ago I was reading more about the operation of rubidium vapour oscillators, and noticed that the ‘filter cell’ is very sensitive to magnetic fields – hence the mu-metal shielding case, and also for the ‘C-tuning’ coil. And I wondered if the main reason why the FE-5680A had apparently worked in China, but wouldn’t lock up in Sydney (Australia) might be caused by the fact that Quangzhou (China) is in the northern hemisphere while I’m ‘down under’ in the southern hemisphere – where the earth’s field is presumably somewhat different, in terms of both strength and direction. So I decided to test this in a crude way, by inverting the FE-5680A and seeing what happened. And – lo and behold – it locked up within 2.5 minutes, and stayed locked until I turned off the power and let it go cold again. The next morning I applied power again, and within 3 minutes it locked up again with no problems. And it’s been locked up now for over 48 hours... My first thought was to make a typical 'down-under' joke and suggest you run the 5680A upside down, but you beat me to it! :) So it seems that the different magnetic field here may have been the problem – either that, or it may have received a ‘jolt’ in transit, which prevented in from locking unless it was inverted. But how do I tell which of these explanations is right, without ‘opening her up’ again and looking for some kind of subtle physical fault? Another idea: perhaps the mu-metal shield case had acquired a small dose of magnetisation in transit (via a physical shock, or from a strong field metal detector). I guess in this case that I would have to remove the two halves of the case, and bake them in a furnace to demagnetise them again. My very limited knowledge regarding mu-metal is that it is so magnetically 'soft' that it can't be magnetized. If it was somehow magnetized, inverting the unit wouldn't make any difference, would it? Or should I just run the FE-5680A upside down permanently – the simple but ‘crude’ answer? I don't believe for a second (pun intended) that the earth's magnetic field has any effect on the locking of your 5680A. It's just not strong enough. The same applies to the C-field which can only nudge the frequency one way or another by a small amount. Since flipping the unit DID make a difference, my money would be on a trivial, boring mechanical issue inside the unit. Could be a bad solder joint, broken wire, floating piece of debris, or something like that. Worst case might be a broken glue joint somewhere in the physics package. That could be ugly. I would definitely open it up and see if anything falls out. I’m not sure if this FE-5680A has the ‘C-tuning’ gizmo fitted, or wired up. Am I right in thinking that another approach might be to try varying the tuning via the RS-232C serial port? Does this work via the C-tuning coil anyway, or by tweaking the DDS? The RS-232 commands affect the DDS - assuming your unit does have one. It will have no effect on the locking, only on the output frequency. A few years ago I bought a dead Datum SLCR Rb standard. It's a cousin to the LPRO. I thought I'd learn some things by trying to fix it. The problem was intermittent. I tore it apart and found that one of the legs of the crystal had never been soldered! Never overlook the obvious. I hope a much more experienced time nut can provide a few answers, please. Maybe the blind leading the blind is a closer description. Ed Jim Rowe ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go
Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia
Thanks for that suggestion too, Mr Kehren. I'll check for dry joints, etc in that region also... Cheers, Jim Rowe -Original Message- From: ewkehren Sent: Saturday, February 08, 2014 12:39 PM To: time-nuts@febo.com Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia Could be the C coil Sent from Samsung tabletEB4APL eb4...@cembreros.jazztel.es wrote:Hi, I second the idea about a mechanical issue. When I opened my FRS-C I found that one of the connector pins had never been soldered, it only made mechanical contact with the PBC. Perhaps it showed an intermittent failure and was retired with low hours. Ignacio EB4APL On 07/02/2014 3:54, Ed Palmer wrote: Hi Jim, On 2/6/2014 3:32 PM, Jamieson (Jim) Rowe wrote: Hi again folks, You may (or may not) recall that a month or so ago, I asked for any information that might be available regarding how to fix a ‘used’ FE-5680A rubidium module from China (via ebay) which was tested by the supplier in China as working OK, but would not seem to lock up to rubidium here in Sydney. There wasn’t a great deal of info available, it seems, so I kept on checking ideas myself – mostly with no luck. The module would never lock, but kept cycling back and forth between about 9.999770MHz and 10.36MHz – ‘searching’ for a lock, but never finding it. Anyway, a couple of days ago I was reading more about the operation of rubidium vapour oscillators, and noticed that the ‘filter cell’ is very sensitive to magnetic fields – hence the mu-metal shielding case, and also for the ‘C-tuning’ coil. And I wondered if the main reason why the FE-5680A had apparently worked in China, but wouldn’t lock up in Sydney (Australia) might be caused by the fact that Quangzhou (China) is in the northern hemisphere while I’m ‘down under’ in the southern hemisphere – where the earth’s field is presumably somewhat different, in terms of both strength and direction. So I decided to test this in a crude way, by inverting the FE-5680A and seeing what happened. And – lo and behold – it locked up within 2.5 minutes, and stayed locked until I turned off the power and let it go cold again. The next morning I applied power again, and within 3 minutes it locked up again with no problems. And it’s been locked up now for over 48 hours... My first thought was to make a typical 'down-under' joke and suggest you run the 5680A upside down, but you beat me to it! :) So it seems that the different magnetic field here may have been the problem – either that, or it may have received a ‘jolt’ in transit, which prevented in from locking unless it was inverted. But how do I tell which of these explanations is right, without ‘opening her up’ again and looking for some kind of subtle physical fault? Another idea: perhaps the mu-metal shield case had acquired a small dose of magnetisation in transit (via a physical shock, or from a strong field metal detector). I guess in this case that I would have to remove the two halves of the case, and bake them in a furnace to demagnetise them again. My very limited knowledge regarding mu-metal is that it is so magnetically 'soft' that it can't be magnetized. If it was somehow magnetized, inverting the unit wouldn't make any difference, would it? Or should I just run the FE-5680A upside down permanently – the simple but ‘crude’ answer? I don't believe for a second (pun intended) that the earth's magnetic field has any effect on the locking of your 5680A. It's just not strong enough. The same applies to the C-field which can only nudge the frequency one way or another by a small amount. Since flipping the unit DID make a difference, my money would be on a trivial, boring mechanical issue inside the unit. Could be a bad solder joint, broken wire, floating piece of debris, or something like that. Worst case might be a broken glue joint somewhere in the physics package. That could be ugly. I would definitely open it up and see if anything falls out. I’m not sure if this FE-5680A has the ‘C-tuning’ gizmo fitted, or wired up. Am I right in thinking that another approach might be to try varying the tuning via the RS-232C serial port? Does this work via the C-tuning coil anyway, or by tweaking the DDS? The RS-232 commands affect the DDS - assuming your unit does have one. It will have no effect on the locking, only on the output frequency. A few years ago I bought a dead Datum SLCR Rb standard. It's a cousin to the LPRO. I thought I'd learn some things by trying to fix it. The problem was intermittent. I tore it apart and found that one of the legs of the crystal had never been soldered! Never overlook the obvious. I hope a much more experienced time nut can provide a few answers, please. Maybe the blind leading the blind is a closer description. Ed Jim Rowe ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman
Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia
Jim, According to my log, my first unit sweeps from 9.999766 to 10.56 and locks in less than 3 min. My second unit sweeps from 9.9997414 to10.493 and also locks in less than 3 min. Probably your unit needs to go a little bit higher. The time spent at the limits probably is not relevant, I also noticed it and that they lock when reaching 10.0 MHz in the same ramp, I don't remember if going up or down. But now that you are able to measure, what are the figures with the unit turned up and down? Regards, Ignacio EB4APL On 09/02/2014 2:57, Jamieson (Jim) Rowe wrote: Hi Magnus, Thanks again for those further suggestions. I do have a GPSDO, and I had been able to use it with a counter to check that the FE-5680A was swinging either side of 10MHz. But I didn't make sure that it was swinging evenly each side of 10MHz . According to my notes it was swinging between 9.999770 and 10.36MHz -- i.e., about 230Hz low and about 36Hz high. But it was spending more of the time below 10MHz than above -- does this suggest to you that I should tweak C217 until it swings by about the same amount either way? Cheers, Jim -Original Message- From: Magnus Danielson Sent: Sunday, February 09, 2014 3:36 AM To: time-nuts@febo.com Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia Hi Jim, On 07/02/14 05:19, Jamieson (Jim) Rowe wrote: Hi Magnus, Thanks for those suggestions also. So if I understand you right, I'd be better off trying to tweak the oscillator tuning -- using the trimcap? Or did you mean via the RS-232C 'offset adjustment' command? I covered this in another message I just sent, but for completeness: You want the C217 trim-cap adjusted such that the lock-in sweep will sweep over 10 MHz, because that's where the synthesized magic locks up and you get 10 MHz out. If you use the offset adjustment, you could possibly get it to lock up, but not producing the 10 MHz you expect. Once you got the trick, it's actually quite fun to trim and get the warm fuzzy feeling of fixing it as it locks up. 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. ___ 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] How I got my FE-5680A to lock in Sydney, Australia
What was the timebase for your counter? I suspect that it is off freq and the Rb is not actually making it above 10 MHz. Inverting the Rb is causing a 2G shift in gravity to the Rb crystal probably shifting its freq enough to cause lock. ___ 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] How I got my FE-5680A to lock in Sydney, Australia
Hi, I second the idea about a mechanical issue. When I opened my FRS-C I found that one of the connector pins had never been soldered, it only made mechanical contact with the PBC. Perhaps it showed an intermittent failure and was retired with low hours. Ignacio EB4APL On 07/02/2014 3:54, Ed Palmer wrote: Hi Jim, On 2/6/2014 3:32 PM, Jamieson (Jim) Rowe wrote: Hi again folks, You may (or may not) recall that a month or so ago, I asked for any information that might be available regarding how to fix a ‘used’ FE-5680A rubidium module from China (via ebay) which was tested by the supplier in China as working OK, but would not seem to lock up to rubidium here in Sydney. There wasn’t a great deal of info available, it seems, so I kept on checking ideas myself – mostly with no luck. The module would never lock, but kept cycling back and forth between about 9.999770MHz and 10.36MHz – ‘searching’ for a lock, but never finding it. Anyway, a couple of days ago I was reading more about the operation of rubidium vapour oscillators, and noticed that the ‘filter cell’ is very sensitive to magnetic fields – hence the mu-metal shielding case, and also for the ‘C-tuning’ coil. And I wondered if the main reason why the FE-5680A had apparently worked in China, but wouldn’t lock up in Sydney (Australia) might be caused by the fact that Quangzhou (China) is in the northern hemisphere while I’m ‘down under’ in the southern hemisphere – where the earth’s field is presumably somewhat different, in terms of both strength and direction. So I decided to test this in a crude way, by inverting the FE-5680A and seeing what happened. And – lo and behold – it locked up within 2.5 minutes, and stayed locked until I turned off the power and let it go cold again. The next morning I applied power again, and within 3 minutes it locked up again with no problems. And it’s been locked up now for over 48 hours... My first thought was to make a typical 'down-under' joke and suggest you run the 5680A upside down, but you beat me to it! :) So it seems that the different magnetic field here may have been the problem – either that, or it may have received a ‘jolt’ in transit, which prevented in from locking unless it was inverted. But how do I tell which of these explanations is right, without ‘opening her up’ again and looking for some kind of subtle physical fault? Another idea: perhaps the mu-metal shield case had acquired a small dose of magnetisation in transit (via a physical shock, or from a strong field metal detector). I guess in this case that I would have to remove the two halves of the case, and bake them in a furnace to demagnetise them again. My very limited knowledge regarding mu-metal is that it is so magnetically 'soft' that it can't be magnetized. If it was somehow magnetized, inverting the unit wouldn't make any difference, would it? Or should I just run the FE-5680A upside down permanently – the simple but ‘crude’ answer? I don't believe for a second (pun intended) that the earth's magnetic field has any effect on the locking of your 5680A. It's just not strong enough. The same applies to the C-field which can only nudge the frequency one way or another by a small amount. Since flipping the unit DID make a difference, my money would be on a trivial, boring mechanical issue inside the unit. Could be a bad solder joint, broken wire, floating piece of debris, or something like that. Worst case might be a broken glue joint somewhere in the physics package. That could be ugly. I would definitely open it up and see if anything falls out. I’m not sure if this FE-5680A has the ‘C-tuning’ gizmo fitted, or wired up. Am I right in thinking that another approach might be to try varying the tuning via the RS-232C serial port? Does this work via the C-tuning coil anyway, or by tweaking the DDS? The RS-232 commands affect the DDS - assuming your unit does have one. It will have no effect on the locking, only on the output frequency. A few years ago I bought a dead Datum SLCR Rb standard. It's a cousin to the LPRO. I thought I'd learn some things by trying to fix it. The problem was intermittent. I tore it apart and found that one of the legs of the crystal had never been soldered! Never overlook the obvious. I hope a much more experienced time nut can provide a few answers, please. Maybe the blind leading the blind is a closer description. Ed Jim Rowe ___ 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] How I got my FE-5680A to lock in Sydney, Australia
The entry in the FE5680 FAQ on this subject may be helpful, if you haven't tried it already. http://ko4bb.com/dokuwiki/doku.php?id=precision_timing:fe5680a_faq#what_if_my_5680a_output_does_not_lock_up_after_several_minutes I have 3 of those units; one did not lock until I adjusted the trim-cap C217 to bring the free-running frequency of the oscillator into range. If you have a reasonably accurate counter you can check if this is the problem or not by seeing if the output frequency (which ramps up and down prior to lock) crosses through 10.00 MHz or not. Mine did not. ___ 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] How I got my FE-5680A to lock in Sydney, Australia
Could be the C coil Sent from Samsung tabletEB4APL eb4...@cembreros.jazztel.es wrote:Hi, I second the idea about a mechanical issue. When I opened my FRS-C I found that one of the connector pins had never been soldered, it only made mechanical contact with the PBC. Perhaps it showed an intermittent failure and was retired with low hours. Ignacio EB4APL On 07/02/2014 3:54, Ed Palmer wrote: Hi Jim, On 2/6/2014 3:32 PM, Jamieson (Jim) Rowe wrote: Hi again folks, You may (or may not) recall that a month or so ago, I asked for any information that might be available regarding how to fix a ‘used’ FE-5680A rubidium module from China (via ebay) which was tested by the supplier in China as working OK, but would not seem to lock up to rubidium here in Sydney. There wasn’t a great deal of info available, it seems, so I kept on checking ideas myself – mostly with no luck. The module would never lock, but kept cycling back and forth between about 9.999770MHz and 10.36MHz – ‘searching’ for a lock, but never finding it. Anyway, a couple of days ago I was reading more about the operation of rubidium vapour oscillators, and noticed that the ‘filter cell’ is very sensitive to magnetic fields – hence the mu-metal shielding case, and also for the ‘C-tuning’ coil. And I wondered if the main reason why the FE-5680A had apparently worked in China, but wouldn’t lock up in Sydney (Australia) might be caused by the fact that Quangzhou (China) is in the northern hemisphere while I’m ‘down under’ in the southern hemisphere – where the earth’s field is presumably somewhat different, in terms of both strength and direction. So I decided to test this in a crude way, by inverting the FE-5680A and seeing what happened. And – lo and behold – it locked up within 2.5 minutes, and stayed locked until I turned off the power and let it go cold again. The next morning I applied power again, and within 3 minutes it locked up again with no problems. And it’s been locked up now for over 48 hours... My first thought was to make a typical 'down-under' joke and suggest you run the 5680A upside down, but you beat me to it! :) So it seems that the different magnetic field here may have been the problem – either that, or it may have received a ‘jolt’ in transit, which prevented in from locking unless it was inverted. But how do I tell which of these explanations is right, without ‘opening her up’ again and looking for some kind of subtle physical fault? Another idea: perhaps the mu-metal shield case had acquired a small dose of magnetisation in transit (via a physical shock, or from a strong field metal detector). I guess in this case that I would have to remove the two halves of the case, and bake them in a furnace to demagnetise them again. My very limited knowledge regarding mu-metal is that it is so magnetically 'soft' that it can't be magnetized. If it was somehow magnetized, inverting the unit wouldn't make any difference, would it? Or should I just run the FE-5680A upside down permanently – the simple but ‘crude’ answer? I don't believe for a second (pun intended) that the earth's magnetic field has any effect on the locking of your 5680A. It's just not strong enough. The same applies to the C-field which can only nudge the frequency one way or another by a small amount. Since flipping the unit DID make a difference, my money would be on a trivial, boring mechanical issue inside the unit. Could be a bad solder joint, broken wire, floating piece of debris, or something like that. Worst case might be a broken glue joint somewhere in the physics package. That could be ugly. I would definitely open it up and see if anything falls out. I’m not sure if this FE-5680A has the ‘C-tuning’ gizmo fitted, or wired up. Am I right in thinking that another approach might be to try varying the tuning via the RS-232C serial port? Does this work via the C-tuning coil anyway, or by tweaking the DDS? The RS-232 commands affect the DDS - assuming your unit does have one. It will have no effect on the locking, only on the output frequency. A few years ago I bought a dead Datum SLCR Rb standard. It's a cousin to the LPRO. I thought I'd learn some things by trying to fix it. The problem was intermittent. I tore it apart and found that one of the legs of the crystal had never been soldered! Never overlook the obvious. I hope a much more experienced time nut can provide a few answers, please. Maybe the blind leading the blind is a closer description. Ed Jim Rowe ___ 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
[time-nuts] How I got my FE-5680A to lock in Sydney, Australia
Hi again folks, You may (or may not) recall that a month or so ago, I asked for any information that might be available regarding how to fix a ‘used’ FE-5680A rubidium module from China (via ebay) which was tested by the supplier in China as working OK, but would not seem to lock up to rubidium here in Sydney. There wasn’t a great deal of info available, it seems, so I kept on checking ideas myself – mostly with no luck. The module would never lock, but kept cycling back and forth between about 9.999770MHz and 10.36MHz – ‘searching’ for a lock, but never finding it. Anyway, a couple of days ago I was reading more about the operation of rubidium vapour oscillators, and noticed that the ‘filter cell’ is very sensitive to magnetic fields – hence the mu-metal shielding case, and also for the ‘C-tuning’ coil. And I wondered if the main reason why the FE-5680A had apparently worked in China, but wouldn’t lock up in Sydney (Australia) might be caused by the fact that Quangzhou (China) is in the northern hemisphere while I’m ‘down under’ in the southern hemisphere – where the earth’s field is presumably somewhat different, in terms of both strength and direction. So I decided to test this in a crude way, by inverting the FE-5680A and seeing what happened. And – lo and behold – it locked up within 2.5 minutes, and stayed locked until I turned off the power and let it go cold again. The next morning I applied power again, and within 3 minutes it locked up again with no problems. And it’s been locked up now for over 48 hours... So it seems that the different magnetic field here may have been the problem – either that, or it may have received a ‘jolt’ in transit, which prevented in from locking unless it was inverted. But how do I tell which of these explanations is right, without ‘opening her up’ again and looking for some kind of subtle physical fault? Another idea: perhaps the mu-metal shield case had acquired a small dose of magnetisation in transit (via a physical shock, or from a strong field metal detector). I guess in this case that I would have to remove the two halves of the case, and bake them in a furnace to demagnetise them again. Or should I just run the FE-5680A upside down permanently – the simple but ‘crude’ answer? I’m not sure if this FE-5680A has the ‘C-tuning’ gizmo fitted, or wired up. Am I right in thinking that another approach might be to try varying the tuning via the RS-232C serial port? Does this work via the C-tuning coil anyway, or by tweaking the DDS? I hope a much more experienced time nut can provide a few answers, please. Jim Rowe ___ 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] How I got my FE-5680A to lock in Sydney, Australia
On 06/02/14 22:32, Jamieson (Jim) Rowe wrote: Hi again folks, You may (or may not) recall that a month or so ago, I asked for any information that might be available regarding how to fix a ‘used’ FE-5680A rubidium module from China (via ebay) which was tested by the supplier in China as working OK, but would not seem to lock up to rubidium here in Sydney. There wasn’t a great deal of info available, it seems, so I kept on checking ideas myself – mostly with no luck. The module would never lock, but kept cycling back and forth between about 9.999770MHz and 10.36MHz – ‘searching’ for a lock, but never finding it. Anyway, a couple of days ago I was reading more about the operation of rubidium vapour oscillators, and noticed that the ‘filter cell’ is very sensitive to magnetic fields – hence the mu-metal shielding case, and also for the ‘C-tuning’ coil. And I wondered if the main reason why the FE-5680A had apparently worked in China, but wouldn’t lock up in Sydney (Australia) might be caused by the fact that Quangzhou (China) is in the northern hemisphere while I’m ‘down under’ in the southern hemisphere – where the earth’s field is presumably somewhat different, in terms of both strength and direction. So I decided to test this in a crude way, by inverting the FE-5680A and seeing what happened. And – lo and behold – it locked up within 2.5 minutes, and stayed locked until I turned off the power and let it go cold again. The next morning I applied power again, and within 3 minutes it locked up again with no problems. And it’s been locked up now for over 48 hours... So it seems that the different magnetic field here may have been the problem – either that, or it may have received a ‘jolt’ in transit, which prevented in from locking unless it was inverted. But how do I tell which of these explanations is right, without ‘opening her up’ again and looking for some kind of subtle physical fault? Another idea: perhaps the mu-metal shield case had acquired a small dose of magnetisation in transit (via a physical shock, or from a strong field metal detector). I guess in this case that I would have to remove the two halves of the case, and bake them in a furnace to demagnetise them again. Or should I just run the FE-5680A upside down permanently – the simple but ‘crude’ answer? I’m not sure if this FE-5680A has the ‘C-tuning’ gizmo fitted, or wired up. Am I right in thinking that another approach might be to try varying the tuning via the RS-232C serial port? Does this work via the C-tuning coil anyway, or by tweaking the DDS? I hope a much more experienced time nut can provide a few answers, please. The magnetic shield can loose it's shielding capabilities. C-field tuning doesn't really change the opportunity for locking, unless your oscillator is on the edge of the locking range, so trimming the oscillator might work. Putting the oscillator upside-down might be the 2G shift needed. This only tells you that you may consider trimming the oscillator. If you have a strong signal, it's usually the crystal oscillator that is too far off the mark for being pulled in. Measure the frequency as it tries to lock-in. If the sweeps is too high or too low then you need to look at that oscillator. 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] How I got my FE-5680A to lock in Sydney, Australia
Hi Jim, On 2/6/2014 3:32 PM, Jamieson (Jim) Rowe wrote: Hi again folks, You may (or may not) recall that a month or so ago, I asked for any information that might be available regarding how to fix a ‘used’ FE-5680A rubidium module from China (via ebay) which was tested by the supplier in China as working OK, but would not seem to lock up to rubidium here in Sydney. There wasn’t a great deal of info available, it seems, so I kept on checking ideas myself – mostly with no luck. The module would never lock, but kept cycling back and forth between about 9.999770MHz and 10.36MHz – ‘searching’ for a lock, but never finding it. Anyway, a couple of days ago I was reading more about the operation of rubidium vapour oscillators, and noticed that the ‘filter cell’ is very sensitive to magnetic fields – hence the mu-metal shielding case, and also for the ‘C-tuning’ coil. And I wondered if the main reason why the FE-5680A had apparently worked in China, but wouldn’t lock up in Sydney (Australia) might be caused by the fact that Quangzhou (China) is in the northern hemisphere while I’m ‘down under’ in the southern hemisphere – where the earth’s field is presumably somewhat different, in terms of both strength and direction. So I decided to test this in a crude way, by inverting the FE-5680A and seeing what happened. And – lo and behold – it locked up within 2.5 minutes, and stayed locked until I turned off the power and let it go cold again. The next morning I applied power again, and within 3 minutes it locked up again with no problems. And it’s been locked up now for over 48 hours... My first thought was to make a typical 'down-under' joke and suggest you run the 5680A upside down, but you beat me to it! :) So it seems that the different magnetic field here may have been the problem – either that, or it may have received a ‘jolt’ in transit, which prevented in from locking unless it was inverted. But how do I tell which of these explanations is right, without ‘opening her up’ again and looking for some kind of subtle physical fault? Another idea: perhaps the mu-metal shield case had acquired a small dose of magnetisation in transit (via a physical shock, or from a strong field metal detector). I guess in this case that I would have to remove the two halves of the case, and bake them in a furnace to demagnetise them again. My very limited knowledge regarding mu-metal is that it is so magnetically 'soft' that it can't be magnetized. If it was somehow magnetized, inverting the unit wouldn't make any difference, would it? Or should I just run the FE-5680A upside down permanently – the simple but ‘crude’ answer? I don't believe for a second (pun intended) that the earth's magnetic field has any effect on the locking of your 5680A. It's just not strong enough. The same applies to the C-field which can only nudge the frequency one way or another by a small amount. Since flipping the unit DID make a difference, my money would be on a trivial, boring mechanical issue inside the unit. Could be a bad solder joint, broken wire, floating piece of debris, or something like that. Worst case might be a broken glue joint somewhere in the physics package. That could be ugly. I would definitely open it up and see if anything falls out. I’m not sure if this FE-5680A has the ‘C-tuning’ gizmo fitted, or wired up. Am I right in thinking that another approach might be to try varying the tuning via the RS-232C serial port? Does this work via the C-tuning coil anyway, or by tweaking the DDS? The RS-232 commands affect the DDS - assuming your unit does have one. It will have no effect on the locking, only on the output frequency. A few years ago I bought a dead Datum SLCR Rb standard. It's a cousin to the LPRO. I thought I'd learn some things by trying to fix it. The problem was intermittent. I tore it apart and found that one of the legs of the crystal had never been soldered! Never overlook the obvious. I hope a much more experienced time nut can provide a few answers, please. Maybe the blind leading the blind is a closer description. Ed Jim Rowe ___ 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] How I got my FE-5680A to lock in Sydney, Australia
I got into trouble once when we got a centrifuge from the US (I'm in Australia) and it didn't work and I suggested to the Yanks that they should have made it revolve in the opposite direction for working S on the equator. The idiots tried this by rewiring the motor and the basket (the large heavy casting that holds stuff to be centrifuged) promply unscrewed itself and nearly came off the shaft. 30Kg of steel about 500mm in diameter spinning at 5000rpm careening round the lab would not be much fun. I never thought that there could actually be a real reason why things stuff up across the equator. Actually the vertical component of the magnetic field here has the opposite sense, which is why compasses made for Europe are unusable in Australia, the card just tries to align itself at 45 deg to the horizontal and refuses to work as it fouls the internals of the mount, so this might make sense. Tom Harris celephi...@gmail.com On 7 February 2014 08:32, Jamieson (Jim) Rowe jimr...@optusnet.com.auwrote: Hi again folks, You may (or may not) recall that a month or so ago, I asked for any information that might be available regarding how to fix a 'used' FE-5680A rubidium module from China (via ebay) which was tested by the supplier in China as working OK, but would not seem to lock up to rubidium here in Sydney. There wasn't a great deal of info available, it seems, so I kept on checking ideas myself - mostly with no luck. The module would never lock, but kept cycling back and forth between about 9.999770MHz and 10.36MHz - 'searching' for a lock, but never finding it. Anyway, a couple of days ago I was reading more about the operation of rubidium vapour oscillators, and noticed that the 'filter cell' is very sensitive to magnetic fields - hence the mu-metal shielding case, and also for the 'C-tuning' coil. And I wondered if the main reason why the FE-5680A had apparently worked in China, but wouldn't lock up in Sydney (Australia) might be caused by the fact that Quangzhou (China) is in the northern hemisphere while I'm 'down under' in the southern hemisphere - where the earth's field is presumably somewhat different, in terms of both strength and direction. So I decided to test this in a crude way, by inverting the FE-5680A and seeing what happened. And - lo and behold - it locked up within 2.5 minutes, and stayed locked until I turned off the power and let it go cold again. The next morning I applied power again, and within 3 minutes it locked up again with no problems. And it's been locked up now for over 48 hours... So it seems that the different magnetic field here may have been the problem - either that, or it may have received a 'jolt' in transit, which prevented in from locking unless it was inverted. But how do I tell which of these explanations is right, without 'opening her up' again and looking for some kind of subtle physical fault? Another idea: perhaps the mu-metal shield case had acquired a small dose of magnetisation in transit (via a physical shock, or from a strong field metal detector). I guess in this case that I would have to remove the two halves of the case, and bake them in a furnace to demagnetise them again. Or should I just run the FE-5680A upside down permanently - the simple but 'crude' answer? I'm not sure if this FE-5680A has the 'C-tuning' gizmo fitted, or wired up. Am I right in thinking that another approach might be to try varying the tuning via the RS-232C serial port? Does this work via the C-tuning coil anyway, or by tweaking the DDS? I hope a much more experienced time nut can provide a few answers, please. Jim Rowe ___ 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] How I got my FE-5680A to lock in Sydney, Australia
Hi Ed, Thanks for those suggestions -- much appreciated. I guess you're right -- if the case was magnetised, inverting the unit wouldn't make any difference. So presumably, the problem is due to a dry joint or similar problem inside, as you suggest, or perhaps the local magnetic field after all (I do have quite a bit of electrical wiring and electronic gear in my work room). All the best, Jim Rowe -Original Message- From: Ed Palmer Sent: Friday, February 07, 2014 1:54 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia Hi Jim, On 2/6/2014 3:32 PM, Jamieson (Jim) Rowe wrote: Hi again folks, You may (or may not) recall that a month or so ago, I asked for any information that might be available regarding how to fix a ‘used’ FE-5680A rubidium module from China (via ebay) which was tested by the supplier in China as working OK, but would not seem to lock up to rubidium here in Sydney. There wasn’t a great deal of info available, it seems, so I kept on checking ideas myself – mostly with no luck. The module would never lock, but kept cycling back and forth between about 9.999770MHz and 10.36MHz – ‘searching’ for a lock, but never finding it. Anyway, a couple of days ago I was reading more about the operation of rubidium vapour oscillators, and noticed that the ‘filter cell’ is very sensitive to magnetic fields – hence the mu-metal shielding case, and also for the ‘C-tuning’ coil. And I wondered if the main reason why the FE-5680A had apparently worked in China, but wouldn’t lock up in Sydney (Australia) might be caused by the fact that Quangzhou (China) is in the northern hemisphere while I’m ‘down under’ in the southern hemisphere – where the earth’s field is presumably somewhat different, in terms of both strength and direction. So I decided to test this in a crude way, by inverting the FE-5680A and seeing what happened. And – lo and behold – it locked up within 2.5 minutes, and stayed locked until I turned off the power and let it go cold again. The next morning I applied power again, and within 3 minutes it locked up again with no problems. And it’s been locked up now for over 48 hours... My first thought was to make a typical 'down-under' joke and suggest you run the 5680A upside down, but you beat me to it! :) So it seems that the different magnetic field here may have been the problem – either that, or it may have received a ‘jolt’ in transit, which prevented in from locking unless it was inverted. But how do I tell which of these explanations is right, without ‘opening her up’ again and looking for some kind of subtle physical fault? Another idea: perhaps the mu-metal shield case had acquired a small dose of magnetisation in transit (via a physical shock, or from a strong field metal detector). I guess in this case that I would have to remove the two halves of the case, and bake them in a furnace to demagnetise them again. My very limited knowledge regarding mu-metal is that it is so magnetically 'soft' that it can't be magnetized. If it was somehow magnetized, inverting the unit wouldn't make any difference, would it? Or should I just run the FE-5680A upside down permanently – the simple but ‘crude’ answer? I don't believe for a second (pun intended) that the earth's magnetic field has any effect on the locking of your 5680A. It's just not strong enough. The same applies to the C-field which can only nudge the frequency one way or another by a small amount. Since flipping the unit DID make a difference, my money would be on a trivial, boring mechanical issue inside the unit. Could be a bad solder joint, broken wire, floating piece of debris, or something like that. Worst case might be a broken glue joint somewhere in the physics package. That could be ugly. I would definitely open it up and see if anything falls out. I’m not sure if this FE-5680A has the ‘C-tuning’ gizmo fitted, or wired up. Am I right in thinking that another approach might be to try varying the tuning via the RS-232C serial port? Does this work via the C-tuning coil anyway, or by tweaking the DDS? The RS-232 commands affect the DDS - assuming your unit does have one. It will have no effect on the locking, only on the output frequency. A few years ago I bought a dead Datum SLCR Rb standard. It's a cousin to the LPRO. I thought I'd learn some things by trying to fix it. The problem was intermittent. I tore it apart and found that one of the legs of the crystal had never been soldered! Never overlook the obvious. I hope a much more experienced time nut can provide a few answers, please. Maybe the blind leading the blind is a closer description. Ed Jim Rowe ___ 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
Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia
Hi Tom, Thanks for your comment, which seems to confirm that the earth's magnetic field (plus the fields associated with my other gear might well be associated with the problem. Perhaps I'd be better off getting hold of a soft steel box to put the complete FE-5680A into, along with its mu-metal shield case... Best regards, Jim Rowe -Original Message- From: Tom Harris Sent: Friday, February 07, 2014 2:31 PM To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia I got into trouble once when we got a centrifuge from the US (I'm in Australia) and it didn't work and I suggested to the Yanks that they should have made it revolve in the opposite direction for working S on the equator. The idiots tried this by rewiring the motor and the basket (the large heavy casting that holds stuff to be centrifuged) promply unscrewed itself and nearly came off the shaft. 30Kg of steel about 500mm in diameter spinning at 5000rpm careening round the lab would not be much fun. I never thought that there could actually be a real reason why things stuff up across the equator. Actually the vertical component of the magnetic field here has the opposite sense, which is why compasses made for Europe are unusable in Australia, the card just tries to align itself at 45 deg to the horizontal and refuses to work as it fouls the internals of the mount, so this might make sense. Tom Harris celephi...@gmail.com On 7 February 2014 08:32, Jamieson (Jim) Rowe jimr...@optusnet.com.auwrote: Hi again folks, You may (or may not) recall that a month or so ago, I asked for any information that might be available regarding how to fix a 'used' FE-5680A rubidium module from China (via ebay) which was tested by the supplier in China as working OK, but would not seem to lock up to rubidium here in Sydney. There wasn't a great deal of info available, it seems, so I kept on checking ideas myself - mostly with no luck. The module would never lock, but kept cycling back and forth between about 9.999770MHz and 10.36MHz - 'searching' for a lock, but never finding it. Anyway, a couple of days ago I was reading more about the operation of rubidium vapour oscillators, and noticed that the 'filter cell' is very sensitive to magnetic fields - hence the mu-metal shielding case, and also for the 'C-tuning' coil. And I wondered if the main reason why the FE-5680A had apparently worked in China, but wouldn't lock up in Sydney (Australia) might be caused by the fact that Quangzhou (China) is in the northern hemisphere while I'm 'down under' in the southern hemisphere - where the earth's field is presumably somewhat different, in terms of both strength and direction. So I decided to test this in a crude way, by inverting the FE-5680A and seeing what happened. And - lo and behold - it locked up within 2.5 minutes, and stayed locked until I turned off the power and let it go cold again. The next morning I applied power again, and within 3 minutes it locked up again with no problems. And it's been locked up now for over 48 hours... So it seems that the different magnetic field here may have been the problem - either that, or it may have received a 'jolt' in transit, which prevented in from locking unless it was inverted. But how do I tell which of these explanations is right, without 'opening her up' again and looking for some kind of subtle physical fault? Another idea: perhaps the mu-metal shield case had acquired a small dose of magnetisation in transit (via a physical shock, or from a strong field metal detector). I guess in this case that I would have to remove the two halves of the case, and bake them in a furnace to demagnetise them again. Or should I just run the FE-5680A upside down permanently - the simple but 'crude' answer? I'm not sure if this FE-5680A has the 'C-tuning' gizmo fitted, or wired up. Am I right in thinking that another approach might be to try varying the tuning via the RS-232C serial port? Does this work via the C-tuning coil anyway, or by tweaking the DDS? I hope a much more experienced time nut can provide a few answers, please. Jim Rowe ___ 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] How I got my FE-5680A to lock in Sydney, Australia
Hi Magnus, Thanks for those suggestions also. So if I understand you right, I'd be better off trying to tweak the oscillator tuning -- using the trimcap? Or did you mean via the RS-232C 'offset adjustment' command? Regards, Jim Rowe -Original Message- From: Magnus Danielson Sent: Friday, February 07, 2014 2:36 PM To: time-nuts@febo.com Subject: Re: [time-nuts] How I got my FE-5680A to lock in Sydney, Australia On 06/02/14 22:32, Jamieson (Jim) Rowe wrote: Hi again folks, You may (or may not) recall that a month or so ago, I asked for any information that might be available regarding how to fix a ‘used’ FE-5680A rubidium module from China (via ebay) which was tested by the supplier in China as working OK, but would not seem to lock up to rubidium here in Sydney. There wasn’t a great deal of info available, it seems, so I kept on checking ideas myself – mostly with no luck. The module would never lock, but kept cycling back and forth between about 9.999770MHz and 10.36MHz – ‘searching’ for a lock, but never finding it. Anyway, a couple of days ago I was reading more about the operation of rubidium vapour oscillators, and noticed that the ‘filter cell’ is very sensitive to magnetic fields – hence the mu-metal shielding case, and also for the ‘C-tuning’ coil. And I wondered if the main reason why the FE-5680A had apparently worked in China, but wouldn’t lock up in Sydney (Australia) might be caused by the fact that Quangzhou (China) is in the northern hemisphere while I’m ‘down under’ in the southern hemisphere – where the earth’s field is presumably somewhat different, in terms of both strength and direction. So I decided to test this in a crude way, by inverting the FE-5680A and seeing what happened. And – lo and behold – it locked up within 2.5 minutes, and stayed locked until I turned off the power and let it go cold again. The next morning I applied power again, and within 3 minutes it locked up again with no problems. And it’s been locked up now for over 48 hours... So it seems that the different magnetic field here may have been the problem – either that, or it may have received a ‘jolt’ in transit, which prevented in from locking unless it was inverted. But how do I tell which of these explanations is right, without ‘opening her up’ again and looking for some kind of subtle physical fault? Another idea: perhaps the mu-metal shield case had acquired a small dose of magnetisation in transit (via a physical shock, or from a strong field metal detector). I guess in this case that I would have to remove the two halves of the case, and bake them in a furnace to demagnetise them again. Or should I just run the FE-5680A upside down permanently – the simple but ‘crude’ answer? I’m not sure if this FE-5680A has the ‘C-tuning’ gizmo fitted, or wired up. Am I right in thinking that another approach might be to try varying the tuning via the RS-232C serial port? Does this work via the C-tuning coil anyway, or by tweaking the DDS? I hope a much more experienced time nut can provide a few answers, please. The magnetic shield can loose it's shielding capabilities. C-field tuning doesn't really change the opportunity for locking, unless your oscillator is on the edge of the locking range, so trimming the oscillator might work. Putting the oscillator upside-down might be the 2G shift needed. This only tells you that you may consider trimming the oscillator. If you have a strong signal, it's usually the crystal oscillator that is too far off the mark for being pulled in. Measure the frequency as it tries to lock-in. If the sweeps is too high or too low then you need to look at that oscillator. 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.
