BG7TBL GPSDO rubidium frequency standards

[Raindog]

Hello all,

Was wondering if anyone out here has tried one of the rubidium GPSDO standards by BG7TBL. I have one of the GPSDO OCXO standards and have been really happy with it. I have been thinking of obtaining one of these because you know, why not.

Best Regards,

Craig Petersen - N7UQA

[bdunham7]

Unless you need to use it without a GPS signal,  I think the performance will actually be a bit worse vs a GPS disciplined OCXO. 

[GigaJoe]

a difference - rubidium more stable in short term. gps ocxo - under influence of voltage correction. I'm watching how phase of gpsdo shifting back and forward comparing to regular ocxo , so it constantly adjusting frequency.
so for a maximum resolution standalone ocxo or rubidium as reference more preferred.  for a regular 8D counter, a well-constructed standalone ocxo , that constantly on state - more then adequate.

[MIS42N]

A rubidium standard needs to be calibrated. For example one advert says '20 year aging less than 0.005 ppm' (or 5 pp billion). I have been building cheap GPSDOs and with good GPS reception and a well burned in OCXO (i.e. running for 2 weeks) it routinely delivers 10MHz to 0.1ppb (the possible drift of a Rubidium in a year).

You can get the best of both worlds by having a cheap GPSDO and using it to calibrate the Rubidium. GPSDOs are usually phase locked to the GPS signal. Typically, divide the 10MHz GPSDO signal to get 1MHz, do the same with the Rubidium, compare the phases over several hours. The GPSDO phase can move back and forth by many nanoseconds (can be over 100 with poor GPS reception) so comparing at 10MHz can be a problem. For instance, if the GPSDO phase is 100ns out at the start of a 3 hour comparison, and 100ns out in the opposite direction at the end of 3 hours, the comparison error is 2 parts in 10^12.

[thinkfat]

Unless you need the inherent stability of a Rb for times when you have no GPS reception, I'd say, not worth it.