Electronics > Beginners
Measuring an OCXO - or not
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metrologist:
I plugged it in on Sept 1st or 2nd, let it settle in and it's been on since. The spec requires 30-day warmup. After a couple weeks, I started playing with the trimpot. It always had an upward drift, so I adjusted it lower an amount based on projected settling. I wasn't sure if I was seeing mechanical relaxing in the trimpot.

edit: it's been on 39 days and the average of the latest 26 daily samples is 7e-10.

I'm not visualizing the DDS approach. Clock a DDS with the OCXO and then make corrections to the DDS output based on feedback from a PPS input?
KE5FX:

--- Quote from: metrologist on October 10, 2018, 09:21:58 pm ---I'm not visualizing the DDS approach. Clock a DDS with the OCXO and then make corrections to the DDS output based on feedback from a PPS input?

--- End quote ---

Yep.
iMo:
There are 48bit DDS chips available. With ~10MHz input the resolution is 35 nanoHertz. You will not get 10MHz output without using the PLL multiplier inside the DDS, however. With 4x10MHz you get 10MHz 14bit sine output with 0.14uHertz resolution.
KE5FX:

--- Quote from: imo on October 11, 2018, 07:32:55 am ---There are 48bit DDS chips available. With ~10MHz input the resolution is 35 nanoHertz. You will not get 10MHz output, however.

--- End quote ---

Sure you can.  Just keep track of the residual frequency error over time and reprogram the DDS to cancel it out.  You can maintain as much precision as you want on the controller.


iMo:
@KE5FX: do you mean a software DDS? Or an external DDS chip?
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