[time-nuts] TBolt OCXO replacement
In the ever ending battle to improve my TBolt's performance, I am in the process of upgrading a OCXO replacement I did to it a while back. It would be Interesting to hear suggestions from others that have done similar sort of things and the results they have achieved. ws ___ 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] TBolt OCXO replacement
At 11:37 AM 2/16/2010 , WarrenS wrote: In the ever ending battle to improve my TBolt's performance, I am in the process of upgrading a OCXO replacement I did to it a while back. It would be Interesting to hear suggestions from others that have done similar sort of things and the results they have achieved. Did you check out John Miles's writeup? http://www.thegleam.com/ke5fx/tbolt.htm ___ 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] TBolt OCXO replacement
Hi A similar question though would be - once you have done all the corrections to the setup of the TBolt (damping, time constant, sensitivity) what's left to fix? I would *guess*: Lower aging Better TC Better short term Aging will likely get better the longer you leave the existing oscillator on power. You also may be able to pick between units to find the best of 4 or something like that. TC can be improved a number of ways simply by helping the existing part. I think we have gone over that in about 300,000 messages so far. Short term stability is about the only thing I can see that's still on the list. That gets you to the question - just how good do you think the 1 second AVAR is on the existing oscillator, independent of the TBolt environment? If for instance you have a 2.5x10^-12 OCXO in yours, you would only see a significant improvement with a sub 1.0x10^-12 OCXO. That sort of bounds your OCXO shopping list right there. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Scott Newell Sent: Tuesday, February 16, 2010 1:06 PM To: time-nuts@febo.com Subject: Re: [time-nuts] TBolt OCXO replacement At 11:37 AM 2/16/2010 , WarrenS wrote: In the ever ending battle to improve my TBolt's performance, I am in the process of upgrading a OCXO replacement I did to it a while back. It would be Interesting to hear suggestions from others that have done similar sort of things and the results they have achieved. Did you check out John Miles's writeup? http://www.thegleam.com/ke5fx/tbolt.htm ___ 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] TBolt OCXO replacement
Timing newbie here, so please educate me - why does aging matter? Isn't the whole purpose of a GPSDO to completely eliminate long-term drift? Thanks Henry On Tue, Feb 16, 2010 at 2:36 PM, Bob Camp li...@cq.nu wrote: Hi A similar question though would be - once you have done all the corrections to the setup of the TBolt (damping, time constant, sensitivity) what's left to fix? I would *guess*: Lower aging Better TC Better short term Aging will likely get better the longer you leave the existing oscillator on power. You also may be able to pick between units to find the best of 4 or something like that. TC can be improved a number of ways simply by helping the existing part. I think we have gone over that in about 300,000 messages so far. Short term stability is about the only thing I can see that's still on the list. That gets you to the question - just how good do you think the 1 second AVAR is on the existing oscillator, independent of the TBolt environment? If for instance you have a 2.5x10^-12 OCXO in yours, you would only see a significant improvement with a sub 1.0x10^-12 OCXO. That sort of bounds your OCXO shopping list right there. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Scott Newell Sent: Tuesday, February 16, 2010 1:06 PM To: time-nuts@febo.com Subject: Re: [time-nuts] TBolt OCXO replacement At 11:37 AM 2/16/2010 , WarrenS wrote: In the ever ending battle to improve my TBolt's performance, I am in the process of upgrading a OCXO replacement I did to it a while back. It would be Interesting to hear suggestions from others that have done similar sort of things and the results they have achieved. Did you check out John Miles's writeup? http://www.thegleam.com/ke5fx/tbolt.htm ___ 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. -- Henry Hallam Sent from my Laptop ___ 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] TBolt OCXO replacement
That gets you to the question - just how good do you think the 1 second AVAR is on the existing oscillator, independent of the TBolt environment? If for instance you have a 2.5x10^-12 OCXO in yours, you would only see a significant improvement with a sub 1.0x10^-12 OCXO. That sort of bounds your OCXO shopping list right there. Several 5061As have been appearing on eBay lately and selling for decent prices in the $400 range, with unknown tube condition. There's no reason to think the tubes are any good, but what I did notice in the photos is that they seem to be late enough models to have the 10811-60109 oscillators installed. I have two of those (one in a working 5061A and one from a dead 5061A which is presently installed in my Thunderbolt) and have just recently been able to start looking at their performance, using a 5065A (which also has a -60109 OCXO). So far I'm impressed. When I disable disciplining in the Thunderbolt, the oscillator tends to stay well below 1E-12 until t=1000 seconds. The one in the 5061A doesn't seem quite as stable, but then it hasn't been enclosed in an unventilated chassis and left on for a couple of months, the way the one in the Thunderbolt has been. I still need to do a couple of overnight runs on that one to see how it behaves. Warren has spent a lot of time tinkering with this Thunderbolt remotely via the Heather server, and has been running it with a 750-second time constant, damping factor 0.75. I want to do some further tests to see what effects the elevation mask and AMU filter have on the actual ADEV performance. It is still falling short of Tom's best HP 58503A clock, but perhaps with some more tweaking we'll get it down below 1E-12 with disciplining turned on. -- john, KE5FX attachment: TBolt_10811_undisc_vs_disc.gif___ 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] TBolt OCXO replacement
Hi Nothing is ever perfect. The magic can only do just so well. The lower the aging rate, the better the result after correction. A little more detail: Take a number, maybe 10 ns and call it the error of the GPS signal. Over a 1 second period, that' s not so good (10 ppb). Over 10,000 seconds (~3 hours) it's better (1 ppt). Wait for a day and it's quite good (0.1 ppt). Wait a couple of weeks and it's tough to beat ( 1.0 x 10^-14). If you take a different number for error all of that will directly scale. The problem is - all of that takes *time*. The more stable the OCXO the better it can smooth out the variations in GPS. That of course assumes that you crank out the time constant of the loop to make that be true. Bob On Feb 16, 2010, at 6:28 PM, Henry Hallam wrote: Timing newbie here, so please educate me - why does aging matter? Isn't the whole purpose of a GPSDO to completely eliminate long-term drift? Thanks Henry On Tue, Feb 16, 2010 at 2:36 PM, Bob Camp li...@cq.nu wrote: Hi A similar question though would be - once you have done all the corrections to the setup of the TBolt (damping, time constant, sensitivity) what's left to fix? I would *guess*: Lower aging Better TC Better short term Aging will likely get better the longer you leave the existing oscillator on power. You also may be able to pick between units to find the best of 4 or something like that. TC can be improved a number of ways simply by helping the existing part. I think we have gone over that in about 300,000 messages so far. Short term stability is about the only thing I can see that's still on the list. That gets you to the question - just how good do you think the 1 second AVAR is on the existing oscillator, independent of the TBolt environment? If for instance you have a 2.5x10^-12 OCXO in yours, you would only see a significant improvement with a sub 1.0x10^-12 OCXO. That sort of bounds your OCXO shopping list right there. Bob -Original Message- From: time-nuts-boun...@febo.com [mailto:time-nuts-boun...@febo.com] On Behalf Of Scott Newell Sent: Tuesday, February 16, 2010 1:06 PM To: time-nuts@febo.com Subject: Re: [time-nuts] TBolt OCXO replacement At 11:37 AM 2/16/2010 , WarrenS wrote: In the ever ending battle to improve my TBolt's performance, I am in the process of upgrading a OCXO replacement I did to it a while back. It would be Interesting to hear suggestions from others that have done similar sort of things and the results they have achieved. Did you check out John Miles's writeup? http://www.thegleam.com/ke5fx/tbolt.htm ___ 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. -- Henry Hallam Sent from my Laptop ___ 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] TBolt OCXO replacement
Henry Hallam wrote: Timing newbie here, so please educate me - why does aging matter? Isn't the whole purpose of a GPSDO to completely eliminate long-term drift? First degree effect yes, but depending on how you do it, more or less of the drift remains uncompensated. If you just try to do frequency compensation, drift is uncompensated and a second-degree PI-regulator will have a phase shift in its chase of frequency and also then a frequency error (it compensates the frequency it had a while ago). Linear drift compensation (such as PII²-regulator) would work better, if only the oscillator had true linear drift... which they don't. Various elaborate algorithms exists to handle both tempco and drift (both important in hold-over operation), the Thunderbolt is not doing too advanced tricks. A low-drifter would certainly help, but to be meaningful tempco also needs to be considered. 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] TBolt OCXO replacement
On Tue, 16 Feb 2010 15:28:11 -0800, Henry Hallam wrote: ... - why does aging matter? Isn't the whole purpose of a GPSDO to completely eliminate long-term drift? Aging? This remembers me on something... .When I get older, losing my hair - ... ...will you still need me, will you still feed me, when... ;-) Oscillators are sometimes well behaving just like humans... slowing down etc... they need a little help... food, pacemaker, something more ? ;-) friendly greetings Arnold ___ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
