Hi Yes, fat fingers strike yet again …
==== I have never seen data on a 5065 run in an altitude chamber. I’ve done the measurements on OCXO’s and may try it on some of the little telecom Rb’s. For small items, it’s a pretty easy test to run. For bigger things, the “pressure vessel” gets a bit harder to lash up. The fiddly part is keeping the temperature constant as the pressure zooms up and down. Bob > On Mar 14, 2016, at 3:20 PM, Lars Walenius <lars.walen...@hotmail.com> wrote: > > Hi > > Shouldn´t 5x10^-11 over 50C be 1x10^-12 / C? So with 2-4°C variation it is > 2-4x10^-12. > > What about pressure variations for the HP5065 and other Rb´s? My LPRO have > about 7x10^-14/mBar (hPa) so with 15-20mbar change, that can happen quite > quick, it is also in the ^-12 range. The tempco for my LPRO is 7x10^-13/°C > and drift in the high ^-14 per day so my GPSDO controller mostly fights the > temperature and pressure variations I think. I like having a GPS disciplined > Rb as I haven´t had to adjust it during the last years. Of course a OCXO > based GPSDO will also stay on frequency. For me the Rb have been good when I > have tested GPS modules and GPSDO´s just out of curiosity. In hold mode it > have been useful to get the ADEV out to say 10000 secs (low ^-13). > > Lars > > Från: Bob Camp<mailto:kb...@n1k.org> > Skickat: den 14 mars 2016 02:01 > Till: Discussion of precise time and frequency > measurement<mailto:time-nuts@febo.com> > Ämne: Re: [time-nuts] HP 5065A repair > > Hi > > Some math: > > 5x10^-11 over 50C > > You have 1x10^-13 / C > > If you have pretty good HVAC you get 2C cycles. On a typical home system, you > get 2X that or more. > > Net is a bump at 2x10^-13 (or more). > > That assumes no hysteresis. (Hint: there always is hysteresis). > > That assumes you have no rate dependent effects. (… they almost always are > present ..). > > If you are at 10X the data sheet level, the bump is more like 2x10^-12 (or > more). Either one will likely show up on a good test plot. > > Can you take care of all this? Of course you can. Does modeling and > correcting all this fall into the “quick and easy fix” category? Nope, not at > all. The thread is about a request for a simple approach to an Rb setup. That > sort of thing does not include fancy models and all sorts of corrections. > > Bob > > > >> On Mar 13, 2016, at 5:10 PM, Poul-Henning Kamp <p...@phk.freebsd.dk> wrote: >> >> -------- >> In message <aabmqmgvvauqc...@smtpout04.dca.untd.com>, cdel...@juno.com >> writes: >> >>> As far a tempco goes, unless your lab swings tens of degrees will you >>> really see it? >> >> Well, I do... >> >> My air-con is far from optimal, but it clearly makes a very obvious >> bump in my AVAR plots. >> >> >> -- >> Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 >> p...@freebsd.org | TCP/IP since RFC 956 >> FreeBSD committer | BSD since 4.3-tahoe >> Never attribute to malice what can adequately be explained by incompetence. >> _______________________________________________ >> 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 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.
