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CMAC STP2390C 10 MHz OCXO oscillator
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JBeale:
In case of interest. I got one of these 10 MHz ovenized oscillators used from ebay about 5 years ago. I see they are still available:
https://www.ebay.com/itm/CMAC-10MHz-ocxo-oscillator-square-wave-sc-cut-STP-2390C-12V/180911738566

AFAICT there is literally no data on it available anywhere online.  The company that made it still has a page https://cmac.com/ but their frequency control products division was sold off to Rakon in 2007. https://www.electronicsweekly.com/news/business/manufacturing/c-mac-sells-frequency-products-business-for-37m-2007-02/
This part may date to well before that. They apparently had an extensive printed catalog back in the day, which may still exist in someone's cardboard box under a bench.

My unit is crudely hand-marked on the side as a 5V part. It will start up and run at that voltage, but the current draw does not drop over time, as you expect from an oven reaching its temperature setpoint, unless you seal the whole thing in a thick styrofoam box.  It runs fine at +9V drawing 84 mA steady-state (when it is in the insulated box).  A thermocouple on the metal case inside the styrofoam reports 61 C surface temp.  The above current ebay listing says it runs on 12V, and I suspect that's more likely the design point. 

Running at +9V input, the output is a square wave between 0 and 4.5 V and the frequency matches a GPSDO 10.0 MHz signal at a control voltage of 1.95 V.
Checking the control voltage between 0 and +5V, the tuning rate is about +3.1 Hz/volt or 0.31 ppm/volt (slightly steeper around 0V and flatter around 5V).

After leaving it running for several days, I compared the 10 MHz OCXO output with a GPSDO output on the scope, and adjusting the control voltage input to keep the edges aligned (a manual PLL) I find the voltage needed varies between 1.9516 and 1.9528 V over a period of 30 minutes, which would be a total frequency change of 3.7E-10. After an hour it is 1.95222 V so there is no obvious drift at this point.  The long-term stability of my Trimble 57964-80 GPSDO (also from ebay) should be better than that as long as it stays locked of course, but I don't have anything else to compare its short-term stability at that level.
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