Sunday, January 17, 2016

Trimble OCXO 65256

Got this unit some time ago during a search on a popular bid site, it's a 10Mhz OCXO (oven controlled crystal oscillator):


Do I need one, NO, in any case it would be good to have one case needed. The idea is to zero beat it against a well know reference source (either GPS or WWV - http://www.nist.gov/pml/div688/grp40/wwv.cfm) and then use it as reference for a frequency counter.

After initial power on, this was the waveform on the output:


Don't know how precise is the scope or the real frequency on power on without a control loop, so at least looks around 600Hz difference between the two equipment's. Open circuit output Vpp is 300mV.

Model/Part Number is Trimble 65256 , there's also a reference TPN 57964-05 (Trimble Part/Number ?) my guess this will be the main board or secondary reference.  I've found no datasheet on the module so went for the 5V recommended  by the seller for power supply (se my previous post on running two LM7805 to power the "beast"). I didn't measured the current consumption, my guess is that will be close to 1A, at least for initial heating.
I've seen other similar modules (not the exact reference) running on 12V, thinking back, that might be a better idea,

Temporary power supply diagram using two LM7805:



The pin-out and size compare against a standard 9V battery:



Still need to implement the control circuit using VREF and VFC, for now it's free running.

Have a nice week!


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