Hi If it’s a 5V supply then indeed 2.5 is a better bet.
Bob > On Dec 24, 2021, at 4:43 AM, Wilko Bulte <[email protected]> wrote: > > The OCXO is powered from the 5V rail of the UCCM, so I wonder how a Vref=5V > would work? A bit of headroom wouod be required to make a reference circuit > work.? > > Wilko > >> On 23 Dec 2021, at 18:15, Bob kb8tq <[email protected]> wrote: >> >> Hi >> >> It’s a pretty good bet that the Vref is 5V >> >> Bob >> >>> On Dec 23, 2021, at 8:42 AM, Wilko Bulte <[email protected]> wrote: >>> >>> hi, >>> >>> I am currently trying to revive a Trimble UCCM-LPS ex-telco GPSDO. >>> The model is a 57963-D according to the PCB silkscreen. >>> >>> Got the board without its OCXO but luckily my stash of surplus I have >>> discovered a Trimble OCXO labeled 72345-86. Given that that OCXO also has a >>> label UCCM-LPS it "should work". >>> >>> Joining the two resulted in: >>> >>> UCCM >syst:status? >>> >>> ------------------------------------------------------------------------------- >>> 57964-86 serial number S35DB68332 firmware ver 1.0.0.1-01 Ext >>> mode >>> ------------------------------------------------------------------------------- >>> Reference Status __________________________ Reference Outputs >>> _______________ >>> XX Ext Ref : [LOS] >>> TFOM 2 FFOM >>> 3 >>> UCCM A Status[OCXO WARMUP] >>> >>>>> GPS: [phase:-2.8E-09, settling] >>> ACQUISITION ...................................................[GPS 1PPS >>> Valid] >>> Tracking: 8 ____ Not Tracking: 3 ________ Time >>> ____________________________ >>> PRN El Az C/N PRN El Az GPS 13:28:51 23 Dec >>> 2021 >>> 15 71 212 37 5 6 195 >>> 24 45 272 43 30 7 85 ANT DLY 77 ns >>> 17 28 97 37 19 19 124 Position >>> ________________________ >>> 13 55 140 38 MODE Hold >>> 14 39 58 39 >>> 23 33 291 44 LAT N 51:xxx >>> 10 17 324 40 LON E 5:xxx >>> 12 7 212 34 HGT +27.54 m >>> (MSL) >>> >>> >>> >>> >>> ELEV MASK 5 deg >>> ------------------------------------------------------------------------------- >>> >>> Command complete >>> >>> Unfortunately it never went GPS locked. Longer story short: the pin of the >>> OCXO that (I think) should produce a Vref for the EFC circuitry produced >>> some random ~ 266mV. >>> >>> A quick experiment learned that the OCXO freq responds to the EFC voltage. >>> So, looks like the Vref circuit in the OCXO has died. >>> >>> Now the question: has anyone a working unit that they can measure the >>> correct Vref voltage from? >>> >>> For now I have fitted a 2.5V LM336 vref and I >>> see the EFC voltage go up and down a bit, with the output freq hovering >>> around 10MHz (+/- 4mHz roughly). >>> >>> tia, >>> Wilko >>> _______________________________________________ >>> time-nuts mailing list -- [email protected] -- To unsubscribe send >>> an email to [email protected] >>> To unsubscribe, go to and follow the instructions there. >> _______________________________________________ >> time-nuts mailing list -- [email protected] -- To unsubscribe send an >> email to [email protected] >> To unsubscribe, go to and follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] -- To unsubscribe send an > email to [email protected] > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
