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.
