A good OCXO left alone. Rbs should have OCXOs inside... On Thu, Jan 12, 2012 at 5:01 PM, John Ackermann N8UR <j...@febo.com> wrote:
> I think you have to define "better," though. A GPSDRbO will have better > holdover performance (e.g., stability when the GPS signal goes away) than > one using an OCXO, but the OCXO is quite likely to have better short term > stability than the Rb. > > If holdover isn't an issue, you need to find the "Allan Intercept Point" > (term stolen from David Mills and NTP) to see where the GPS and oscillator > ADEV curves cross over. That will tell you how long a loop time constant > you want, and will let you look at the combined ADEV for each type of > oscillator. You may find that a decent OCXO gives better performance > overall than an Rb. > > John > ---- > > > On 1/12/2012 10:37 AM, ewkeh...@aol.com wrote: > >> with the good long term performance of Rb's and the presently available >> 5680A for $ 40 a Shera Type controller will make available to any one on >> the >> list a reference better than a Tbolt for less money than a Tbolt. >> Repeating >> my self I would also add a "clean up" OCXO in order to get the very best. >> Bert Kehren >> >> >> In a message dated 1/12/2012 8:34:54 A.M. Eastern Standard Time, >> jlt...@att.net writes: >> >> David, >> >> I have been following discussions on the list about a GPSDRbO for a year >> or >> so. Some interesting challenges and probably best implemented in a >> 'stable' >> environment rather than portable operation but as best I can tell, it >> would >> require a very stable and good antenna location, stable and clean power, >> and >> I was thinking of using something like an LPRO-101 with an Ext C Field >> input, a Shera type controller, and a GPS timing receiver, though, I >> suspect >> there are likely to be some 'multi-tasking' receivers out there that will >> look at several sources including GPS, GLOSNASS, etc. >> >> While the project might be fun, for portable work, it is likely far >> easier >> and probably just as good (almost), to use a Tbolt. >> >> In any event, something to think about for the future. >> >> Joe >> >> -----Original Message----- >> From: time-nuts-boun...@febo.com >> [mailto:time-nuts-bounces@**febo.com<time-nuts-boun...@febo.com>] >> On >> Behalf Of David >> Sent: Wednesday, January 11, 2012 11:12 PM >> To: Discussion of precise time and frequency measurement >> Subject: Re: [time-nuts] FE-5680A Mechanical Question >> >> >> How would a GPSDRbO work? Phase lock the DDS output to the GPS? Phase >> lock >> a VCXO to the GPS and then phase lock to the RbO on loss of GPS lock? >> >> On Wed, 11 Jan 2012 22:55:58 -0600, "J. L. Trantham"<jlt...@att.net> >> wrote: >> >> Bill, Brian, Bill, and Peter, >>> >>> Thanks for the info. All I need now is a 'project' to incorporate the >>> unit into. >>> >>> In the back of my mind, I have the thought of a 'box' that will be >>> battery powered or 110 VAC powered (perhaps with an internal SLA >>> battery) and include a GPSDO and Rb unit (possibly a GPSDRbO) for the >>> purpose of a 'reference' for portable operation in the microwave >>> regions. >>> >> >> ______________________________**_________________ >> time-nuts mailing list -- time-nuts@febo.com >> To unsubscribe, go to >> https://www.febo.com/cgi-bin/**mailman/listinfo/time-nuts<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<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<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<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.