Rick is right. The effect you see when turning your GPSDO upside down will be predominantly the direct gravitational effect on the OCXO crystal and its mountings. You see this with any OCXO, and the good ones will have a '2G turnover' or other G rating quoted.
For example, the well known HP 10811A specification says 'Gravitational Field: <4 x 10^-9 for 2g static shift (turnover). That's fairly typical. I just measured the effect on a good C-MAC 10MHz OCXO (similar to those used in many recent GPSDOs) and measured 40mHz p-p, or exactly 4e-9. It's complicated in the GPSDO because the correction mechanism (via GPS 1pps) is much slower than the rate at which you can change the gravitational effect. Rb references simply have a faster loop and will correct the G effect more quickly. Murray _______________________________________________ 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.
