Hi
On Dec 9, 2012, at 9:07 PM, WB6BNQ <[email protected]> wrote: > Bob, > > I don't know where you got your multiple versions. Quite possibly from having spent the last 40 years in the business of designing and building OCXO's. > RETRACE deals with the object in a fully realized steady state operating > condition, then removal of power for a period of time (usually stated in real > specs as 24 hours) and then re application of power with a stated result. > Really quite simple in concept. > > Its cousin, WARMUP, would describe a similar process assuming both are at a > non operating nominal environment ambient temperature. Usually a RETRACE > spec will state some amount of off period, like 24 hours. Unless we are > talking super hot molten metal or a nuclear reaction, usually most things get > to nominal room temperature inside of 24 hours. So, in that case RETRACE and > WARMUP would mean virtually the same Except that you see them as independent specifications on OCXO's talking about different parts of the process. Bob > thing. > > Bill....WB6BNQ > > > Bob Camp wrote: > >> Hi >> >> That's one interpretation and one method of measurement. The other method is >> to measure frequency shift from say one hour after power on to 24 hours >> after power on. A lot depends on the requirements of the system the OCXO was >> intended to be used in. >> >> If you use the measure / power off / warmup / measure approach, you need to: >> >> 1) Define the time on before the first measure >> 2) Define the power off time >> 3) Define the warmup time >> >> Change any of those numbers and the retrace number will be different. >> Generally the temperature(s) involved are also defined. The most common case >> is that all of this is done at 20 or 25C. >> >> Bob >> >> On Dec 9, 2012, at 8:47 PM, "Tom Miller" <[email protected]> wrote: >> >>> So if I understand it, you allow the OCXO several days of warm-up to set >>> the frequency. Then when turned off for a while, then restarted. After some >>> warm-up period, the retrace spec would give an indication of how close the >>> frequency will be? >>> >>> Thanks, >>> Tom >>> >>> ----- Original Message ----- From: "Bob Camp" <[email protected]> >>> To: "Discussion of precise time and frequency measurement" >>> <[email protected]> >>> Sent: Sunday, December 09, 2012 7:58 PM >>> Subject: Re: [time-nuts] Switching oscillators >>> >>> >>> Hi >>> >>> Retrace assumes that the oscillator has some "normal" frequency that only >>> moves according to the aging rate. Retrace occurs after the oscillator has >>> been off power for some period. The rate of change is greater than the >>> aging rate. Warmup and retrace are obviously inter-related. Warmup is >>> generally described as a short term (sub 1 hour) process. Retrace is often >>> looked at as a day to multiple day sort of thing. >>> >>> Since none of this is tightly defined, you will see various specs looking >>> at the same issues a bit differently. Often those differences roll up to >>> some sort of system requirement. >>> >>> Bob >>> >>> >>> On Dec 9, 2012, at 7:45 PM, "Tom Miller" <[email protected]> wrote: >>> >>>> Hi Bob, >>>> >>>> Can you give a good definition of retrace as it applies here? >>>> >>>> Thanks, >>>> Tom >>>> >>>> >>>> ----- Original Message ----- From: "Bob Camp" <[email protected]> >>>> To: "Discussion of precise time and frequency measurement" >>>> <[email protected]> >>>> Sent: Sunday, December 09, 2012 7:24 PM >>>> Subject: Re: [time-nuts] Switching oscillators >>>> >>>> >>>> Hi >>>> >>>> Your TCXO will have the same sort of retrace issues as your OCXO. Past >>>> some number of minutes (5,10,15…) you will always be better with a modern >>>> OCXO than with a TCXO. >>>> >>>> Bob >>>> >>>> On Dec 9, 2012, at 7:05 PM, WB6BNQ <[email protected]> wrote: >>>> >>>>> Hi Joe, >>>>> >>>>> I think you all are not looking at this correctly. >>>>> >>>>> 1. First, as has been pointed out, a TCXO will vary around till the >>>>> environment it is in has returned to its nominal operating temperature. >>>>> >>>>> 2. A typical TCXO is nominally spec'ed around +/- 0.5 x 10-7 >>>>> neighborhood. Not a stellar number. >>>>> >>>>> 3. The real spec to look at is the "RETRACE" factor of a good OCXO. >>>>> >>>>> Many of the modern PCB CAN manufactures do not or are quite hazy on >>>>> this point. Vectron, for example, on their double oven high >>>>> performance WIDGET (model DX-170) claims a warmup time of 5 minutes >>>>> to +-10ppb of final frequency, however, they also include this >>>>> cryptic statement "(1 hour reading) @ +25DEGC" on the same spec. I >>>>> am not sure, but it suggests that they are reading the final >>>>> frequency at the one hour point after turn-on. Taking it at face >>>>> value, it suggest that the oscillator is within +/- 1 x 10-8 at 5 >>>>> minutes. That is a whole decade better than the TCXO under any >>>>> condition. >>>>> >>>>> Looking at something real like the HP 10811A/B Quartz Crystal >>>>> Oscillator, you will see they spec the retrace as "Warmup 10 min. >>>>> after turn-on within 5 X 10-9 of final value, at 25DEGC and 20 Vdc. >>>>> See Notes 1 & 2. Notes: 1. For oscillator off-time less than 24 >>>>> hours. 2. Final value is defined as frequency 24 hours after >>>>> turn-on." Here, we are talking about two whole decades better than >>>>> the TCXO ever could be. >>>>> >>>>> 4. So the real question is just what the hell are you doing at 10 >>>>> minutes or less that would require all this worry ? ? >>>>> >>>>> 5. The real answer to your dilemma is to have some serious battery >>>>> backup and if it is truly to be considered a critical necessity, then >>>>> maybe you need a power generator that is automatic when the shore power >>>>> drops. >>>>> >>>>> My two cents, >>>>> >>>>> Bill....WB6BNQ >>>>> >>>>> Joseph Gray wrote: >>>>> >>>>> For my use, I don't think the switching glitch will be a concern. >>>>> Most >>>>> of the time, the equipment will be in a standby mode. There is a >>>>> high >>>>> probability that the OCXO will be in use most of the time. >>>>> >>>>> I guess my original idea of simply waiting a sufficient time for the >>>>> OXCO to warm up and then switching is probably the thing to do. >>>>> >>>>> Joe >>>>> >>>>> On Sun, Dec 9, 2012 at 3:16 PM, Bob Camp <[email protected]> wrote: >>>>>> Both would need some sort of timer to drive them. Both would >>>>> disrupt the instrument when the switch took place. I know of no >>>>> "cheap / easy" ways to take care of the switching glitch. There are >>>>> fancy / expensive ways. >>>>>> >>>>>> Bob >>>>> >>>>> _______________________________________________ >>>>> time-nuts mailing list -- [email protected] >>>>> To unsubscribe, go to >>>>> [1]https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>> and follow the instructions there. >>>>> >>>>> References >>>>> >>>>> 1. https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>> _______________________________________________ >>>>> time-nuts mailing list -- [email protected] >>>>> To unsubscribe, go to >>>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>>> and follow the instructions there. >>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>>> >>>> >>>> >>>> _______________________________________________ >>>> time-nuts mailing list -- [email protected] >>>> To unsubscribe, go to >>>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>>> and follow the instructions there. >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >>> >>> >>> >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] >>> To unsubscribe, go to >>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >>> and follow the instructions there. >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
