Re: [time-nuts] Counter OCXO behaviour
Il 2013-01-14 22:15 Charles P. Steinmetz ha scritto: Because the oscillators are sealed assemblies, I'm not aware of anyone who has taken one apart for analysis -- so the reason for this behavior must be considered unknown until we know what is going on inside. By the way, there is a non working unit on ebay in US just now, 58h to auction end. If it was in EU I would have picked it up just for dissection. Unfortunately for me shipping charges are a little high for an autopsy: ebay #251211816860 Best regards, Charles Fabio. ___ 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] Counter OCXO behaviour
Yes the 1992 4E adjustment is a bear. Mine behaves pretty much the same, ISTR it took me a few days to get it adjusted to my satisfaction and it was still drifting a bit. Interestingly I saw a 1992 with a built in Rb on eBay (I think in France) some years back but the price went way beyong my budget. Dave -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Fabio Eboli Sent: 14 January 2013 23:09 To: Discussion of precise time and frequency measurement Subject: Re: [time-nuts] Counter OCXO behaviour I answer here to all, thank Ed David and Charles for your thoughts. David, LOL, you posted the pic of the exact counter in question. Not a similar unit, I mean it's exactly *that* 1992 that is being measured ;) ___ 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] Counter OCXO behaviour
re ebay #251211816860 the seller is one I've dealt with a few times before, and had excellent service. I would not hesitate to deal with them again. FWIW according to the US Post Office web site a 1 pound package to Italy ships for $11.60. Bob L. - Original Message From: Fabio Eboli fabi...@quipo.it To: Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tue, January 15, 2013 9:21:21 AM Subject: Re: [time-nuts] Counter OCXO behaviour By the way, there is a non working unit on ebay in US just now, 58h to auction end. If it was in EU I would have picked it up just for dissection. Unfortunately for me shipping charges are a little high for an autopsy: ebay #251211816860 Fabio. ___ 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] Counter OCXO behaviour
Robert, I asked the seller for the least expensive way to send that OCXO here (nothing to lose on a marginal packaging, let's assume the item is non working) and he quoted 12USD. I think I must refrain from spending 20USD (assuming I will be the only bidder) for a device to be dissected, althoug I've done worse things with my ebay account :) If it was a working OCXO I would have happily bought it, but thinking about it I would not dissect a working OCXO, for me it would be a crime :) I will see if he has something interesting (and light) in other items he listed, maybe I could share shipping cost between items. Il 2013-01-15 15:34 Robert LaJeunesse ha scritto: re ebay #251211816860 the seller is one I've dealt with a few times before, and had excellent service. I would not hesitate to deal with them again. FWIW according to the US Post Office web site a 1 pound package to Italy ships for $11.60. Bob L. ___ 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] Counter OCXO behaviour
Il 2013-01-15 15:31 David C. Partridge ha scritto: Yes the 1992 4E adjustment is a bear. Mine behaves pretty much the same, ISTR it took me a few days to get it adjusted to my satisfaction and it was still drifting a bit. The strange thing is that mine now is changing frequency at more than 1x10^-10 per day, measuring a 10MHz reference this would be one digit per day, but before it was steady on last digit for long time intervals, last digit moved up and down only with day/night temperature variation. Is it possible that the OCO was sealed by so much time, opening it I changed the internal equilibrium? (humidity?). Interestingly I saw a 1992 with a built in Rb on eBay (I think in France) some years back but the price went way beyong my budget. I've about this on this list, option 04R: http://www.febo.com/pipermail/time-nuts/2011-November/060516.html Fabio. ___ 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] Counter OCXO behaviour
Fabio, I'm glad to see that their shipping charge is fair. Turns out it is only about a dollar more than the shipping to my place here in the states. I did notice that the schematic for the oscillator's small PCB, the 5MHz to 10MHz doubler, is on KO4BB's site (page 22 of the PDF): http://www.ko4bb.com/Manuals/Racal/Racal-Dana_1991-1992-ServiceManualSch.pdf Makes me wonder if the oscillator is good, but the doubler has failed. If so, the unit might be easily salvageable. As for what's in the sealed can, here's hoping you end up with one, somehow, at a cost you are happy with. Bob - Original Message From: Fabio Eboli fabi...@quipo.it To: Robert LaJeunesse lajeune...@mail.com; Discussion of precise time and frequency measurement time-nuts@febo.com Sent: Tue, January 15, 2013 10:04:37 AM Subject: Re: [time-nuts] Counter OCXO behaviour Robert, I asked the seller for the least expensive way to send that OCXO here (nothing to lose on a marginal packaging, let's assume the item is non working) and he quoted 12USD. I think I must refrain from spending 20USD (assuming I will be the only bidder) for a device to be dissected, althoug I've done worse things with my ebay account :) If it was a working OCXO I would have happily bought it, but thinking about it I would not dissect a working OCXO, for me it would be a crime :) I will see if he has something interesting (and light) in other items he listed, maybe I could share shipping cost between items. Il 2013-01-15 15:34 Robert LaJeunesse ha scritto: re ebay #251211816860 the seller is one I've dealt with a few times before, and had excellent service. I would not hesitate to deal with them again. FWIW according to the US Post Office web site a 1 pound package to Italy ships for $11.60. Bob L. ___ 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] Counter OCXO behaviour
Hello, recently I tried to trim the Racal Dana 1992 04E internal reference, using the GPS pps as a reference. I'd like to ask a pair of questions... - First is about the method. I'm using the counter TI to measure it's own OCXO. The GPS is starting the count, the internal reference 10MHz (on the rear there is a reference output connector) stops the count and I log the result as I've done before with other oscillators. Is this a correct procedure? - Second, is about the behaviour of the OCXO after trimming. The OCXO seem not that stable after the trimming, like if the crystal started to age faster than before trimming, and now is slowly stabilizing. It's like the retrace of the crystals I've read about, but the instrument was never powered down in the last month. And it's oven has been on for the last year. Will a crystal retrace also after retrimming? The frequency of the crystal is slowing, in the first hours after the trimming rapidly, and now more slowly. After few days the frequency seem to be slowing somewhere around 1x10^-10 per day. Unfortunately I havent logged the counter for enough time before the trimming, but it measured the same Rb with less than 3 digits of difference (3x10^-10) in last 6 monthes. Thanks, Fabio. ___ 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] Counter OCXO behaviour
Is it manually adjusted right at the oscillator? If so, just opening it up and sticking a screwdriver in there gives it a thermal shock, and the adjusted element will have mechanical stress that has to settle out too - the value can change for a while. Ed ___ 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] Counter OCXO behaviour
The Racal Dana 1991/1992 OCXO has a big pair of pan head screws exposed on the back. One is coarse adjust and one is fine adjust. I have the TCXO version which also exposes the adjustment on the back so you do not have to open anything to get to it. You can see them here: http://www.eevblog.com/forum/reviews/racal-dana-1992-teardown/?action=dlattach;attach=20937;image;PHPSESSID=a5230a2beafd27b99c07580940fe1574 On Mon, 14 Jan 2013 12:34:04 -0800, Ed Breya e...@telight.com wrote: Is it manually adjusted right at the oscillator? If so, just opening it up and sticking a screwdriver in there gives it a thermal shock, and the adjusted element will have mechanical stress that has to settle out too - the value can change for a while. Ed ___ 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] Counter OCXO behaviour
On Mon, 14 Jan 2013 21:14:23 +0100, Fabio Eboli fabi...@quipo.it wrote: Hello, recently I tried to trim the Racal Dana 1992 04E internal reference, using the GPS pps as a reference. I'd like to ask a pair of questions... - First is about the method. I'm using the counter TI to measure it's own OCXO. The GPS is starting the count, the internal reference 10MHz (on the rear there is a reference output connector) stops the count and I log the result as I've done before with other oscillators. Is this a correct procedure? I just measured the GPS pulse output directly with the counter. I got the same calibration results measuring frequency or period. With time interval, I used the delay feature to set the minimum measurement duration. - Second, is about the behaviour of the OCXO after trimming. The OCXO seem not that stable after the trimming, like if the crystal started to age faster than before trimming, and now is slowly stabilizing. It's like the retrace of the crystals I've read about, but the instrument was never powered down in the last month. And it's oven has been on for the last year. Will a crystal retrace also after retrimming? The frequency of the crystal is slowing, in the first hours after the trimming rapidly, and now more slowly. After few days the frequency seem to be slowing somewhere around 1x10^-10 per day. Unfortunately I havent logged the counter for enough time before the trimming, but it measured the same Rb with less than 3 digits of difference (3x10^-10) in last 6 monthes. My 1992 has the TCXO and I noticed the least significant digit drifting after trimming. At least with the 1992 TCXO, I decided the last digit was not worth worrying about which is pretty much the case with all of my other counters although my 1992 is about the best of my bunch. ___ 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] Counter OCXO behaviour
Ed wrote: Is it manually adjusted right at the oscillator? If so, just opening it up and sticking a screwdriver in there gives it a thermal shock, and the adjusted element will have mechanical stress that has to settle out too - the value can change for a while. The 04E standard used in the military surplus 1992s (which are by far the most common 1992s in the US) is typically labeled 9462 454879, Rev. A. There has been a fair bit of discussion on the list about these -- a search of the archive will turn up a number of threads. Yes, they do tend to take a long while to settle after adjustment. So long, in fact -- and with oscillatory gyrations above and below the starting frequency -- that I have speculated on-list that the adjustment may not be a direct adjustment of the tuned circuit (e.g., with the usual capacitor on the crystal), but rather an adjustment to the oven controller setting the crystal temperature. Because the oscillators are sealed assemblies, I'm not aware of anyone who has taken one apart for analysis -- so the reason for this behavior must be considered unknown until we know what is going on inside. 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] Counter OCXO behaviour
I answer here to all, thank Ed David and Charles for your thoughts. David, LOL, you posted the pic of the exact counter in question. Not a similar unit, I mean it's exactly *that* 1992 that is being measured ;) The pictures on eevblog show the early measurements I made with the counter. One of the Rb wasmeasured to about 10MHz+60mHz. After a while (I think a pair of monthes) the reading was slightly over 10MHz+70mHz and remained there for more than 6 monthes, until I trimmed the counter few days ago. The trimming is very touchy, and the simple opening of the screw on the rear is traumatic: the frequency rises for a pair of minutes and then it takes a while to return to the previous level. Talking about this OCXO, how much is it good? I mean for who has eperience with many OCXO is this a good unit, or it's an average one? Is this the kind of stability and reaction that can be expected by an OCXO useful for GPSDO (less the EFC control of course)? Measuring this OCXO, just now I'm starting to feel the precision of the FE5680, or 5682. It's so easy to set the Rb to follow GPS closely for days... I have some pics of the measurements I made, they are a little messy, I hope can be fun and interesting to see: This was before touching anything, top right the phase between the GPS and OCXO: http://www.flickr.com/photos/14336723@N08/8382126024/ it was slow by about 7x10^-9. This was the first trim attempt: http://www.flickr.com/photos/14336723@N08/8382125734/ and this the last trims, the dips in phase are evident, they happen when I open the calibration screw on the rear: http://www.flickr.com/photos/14336723@N08/8381043177/ and at last these are logged after last trim action: http://www.flickr.com/photos/14336723@N08/8381044033/ I tried to extract more data from last log: http://www.flickr.com/photos/14336723@N08/8382126108/ Here I made the first and second derivative in time of the phase, data are heavily averaged, so are not very accurate. The 10MHz period error (vs. GPS) changed from -0.8x10^-10 soon after the trim, to +1x10^-10 after two days (top right). The OCXO period was rising from almost 2x10^-15 soon after the trim to 1.3x10^-15 after two days (bottom left). Seem the stabilization will take a while... Fabio. ___ 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] Counter OCXO behaviour
Il 2013-01-15 00:08 Fabio Eboli ha scritto: Trying to be more clear: 10MHz period error (vs. GPS) changed from -0.8x10^-10 soon after the trim, to +1x10^-10 after two days (top right). Top right is change of phase in time, i.e. period error measured using GPS as reference. The OCXO period was rising from almost 2x10^-15 soon after the trim to 1.3x10^-15 after two days (bottom left). Bottom left is change of period error in time, 1.3x10^-15 per second is around 1.1x10^-10 per day, if I'm not mistaken, more than typical unit's aging stated by datasheet. Seem the stabilization will take a while... Fabio. ___ 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.
