Hi They have a VCXO in the loop. It probably does not have much over +/- 50 Hz of useful range.
Bob On Jan 11, 2012, at 8:32 PM, [email protected] wrote: > My observations are that the RS232 offset on these needs to be considered > as very much a fine adjustment only, and presumably just intended to pull > the frequency on to 10 MHz rather than to provide a usable offset. > > I did try pushing my first unit to the extremes of the adjustment range > shown in the manual and it didn't like it, the frequency was highly unstable > and at one extreme it just gave up and rejected the offset. > > Observations on three units so far indicate that none seem to have had any > offset programmed in the field but all are less stable the further they are > from being set to 10MHz. > > I haven't recorded any long term data as yet, just observed the short term > stability on an HP 53132A and Tek FCA3100 clocked against one of three > T'bolts, but am getting a definite impression that 10MHz is a sweet spot and > that anything either side is just begging to be corrected:-) > > Regards > > Nigel > GM8PZR > > > > > > In a message dated 12/01/2012 01:04:03 GMT Standard Time, [email protected] > writes: > > More observations. My unit is S/N 0316 61953, UN 63983. If I try to > change the > offset count (using RS232) by more than about 131,000 counts (0x20000) at > a time > it sometimes loses the 1PPS and the lock signal goes high. > > By bringing the offset count up slowly (increments of 0x10000) I recorded > the > following drift rates versus offset count: > > 0 usec / sec at 0 > 1 usec / sec at 1441792 (0x160000) > 2 usec / sec at 2949120 (0x2D0000) > 3 usec / sec at 4390912 (0x430000) > 4 usec / sec at 5898240 (0x5A0000) > > The offset count was incremented in units of 0x10000 (65,536) counts so the > drifts are approximate. > > A plot of these results is here: > > http://c-c-i.com/node/161 > > My unit appears to have an adjustment resolution of about 6.8E-13 / count - > close to what has been reported here before. > > > _______________________________________________ > 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.
