Karen, a good double oven OCXO such as Morion etc will give you much better short term stability than most Rudidiums can give you. By a factor of 10 or even 100 sometimes below 10s measurement interval. The Rb's are better anywhere from 100s to many 1000 seconds. bye, Said In a message dated 10/27/2014 13:57:14 Pacific Daylight Time, [email protected] writes:
Many thanks for all your recommendations. Let me provide more details for understanding of my task. I am playing with a GPSDO project on base of uBlox NEO-7M (http://www.ra3apw.ru/ublox-neo-7m-ocxo-gpsdo/) - sorry, text in Russian. One of the main step – ADEV measurement of a developed GPSDO. My ADEV measure stand consists of a frequency counter Pendulum CNT-91 with TimeBase option 19 + GPIB interface + KE5FX TimeLab software (TNX again John). As option for CNT-91’s reference source I can use a homemade GPSDO on base of G3RUH design. IMHO, in this condition a frequency stability of my GPSDO project should be higher than a stability of CNT-91’s reference OCXO. Taking into account that rubidium source has a better short range stability than OCXO or GPSDO I hope to find an external rubidium as 10 MHz reference source instead of internal OCXO of counter. If my reasoning is not right could you please correct them as I am not an expert in this area. Karen, ra3apw > Date: Sun, 26 Oct 2014 14:45:00 -0700 > From: Brooke Clarke <[email protected]> > > Hi Karen: > > The ones you mention are all stand alone Rb oscillators that need to be > calibrated to set their frequency. > This was the historical way that crystal oscillators were calibrated every year > or so. The great advantage of Rb over crystal oscillators is that their drift is > specified in months instead of days. > > A much better - more modern idea - is the GPS Disciplined Oscillator (GPSDO). > It keeps the oscillator "calibrated" in real time. > A popular crystal based GPSDO is the Trimble ThunderBolt: > http://www.prc68.com/I/ThunderBolt.shtml > > Another crystal based GPSDO is the HP Z3805: > http://www.prc68.com/I/Z3805A.html > > There are many more commercial GPSDOs and this list has discussions that > show they can be a do it yourself project for under maybe $10, but require a > number of sophisticated skills. > > I have the just released LTE-Lite GPSDO Evaluation Kit with 10MHz TCXO on > order. Seems to offer good performance for the dollar. > http://www.ebay.com/itm/171504585820 > > The only advantage of a Rb GPSDO over a crystal GPSDO is for the case > where the GPS updating has not happened for some time. > This might be due to a power failure lasting some days or that the oscillator > will be used where there's no GPS access and it only gets "calibrated" then > used much later. > > The Stanford Research PRS-10 Rb oscillator can be used stand alone where it > time stamps an external 1 Pulse Per Second input, or as part of a GPSDO > where an external GPS receiver supplies it with a 1 PPS input. > http://www.prc68.com/I/PRS10.shtml > > The Thunderbolt can be custom modified to drive an external Rb oscillator, > like the ones you mentioned, but that requires some technical sophistication. > > Note the ThunderBolt and Z3805 are complete GPSDOs in a box, just connect > power and a GPS antenna. > The PRS-10 requires an external GPS receiver and antenna. A a practical > matter that means it's more work to maintain the PRS-10 because there's > more opportunity for problems like disconnecting a cable. > > PS Stanford Research offered a version of their SR620 Time Interval counter > that included a Rb oscillator (not a GPSDO) that some government agencies > purchased, but for normal use you really don't need a Rb oscillator, so the > CNT-91R appears to be a similar way so sell it to a government with a lot of > money to spare. So don't feel pressured to use an Rb oscillator. > http://www.prc68.com/I/TandFTE.shtml#SR620 > Mail_Attachment -- > Have Fun, > > Brooke Clarke, N6GCE > http://www.PRC68.com > http://www.end2partygovernment.com/2012Issues.html > http://www.prc68.com/I/DietNutrition.html _______________________________________________ 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.
