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 - 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!


Unknown said...

My Trimble 65256 doesn't work properly on 5V (as advertised), it won't startup. The ref output is 1.8V. If I make the voltage a little higher (up to 7 V) it works and the ref is now stable at 2.55V. So it is a 12V version and not 5V. Output stays about 4 Vpp, even if Uin is up to 10V. On some sites you see that indeed 12V is used.


Ricardo - CT2GQV said...

Hello Walter,
Thank you for the comment.
Mine is in fact a 5v since I have a good output at that Vcc.
The only situation is being already out of spec from the 10Mhz, so not using it at the moment.

73 de Ricardo / CT2GQV