[time-nuts] OCXO Voltage Input?

Bob Camp kb8tq at n1k.org
Thu Sep 4 17:43:20 EDT 2014


The EFC pin *might* have a bypass cap on it. If you drive it with an op-amp an isolating resistor might be needed. If so, a couple hundred ohms is likely enough to stabilize the op-amp.

In a closed loop / control loop setting, the noise on the EFC will be whatever the loop generates. As long as you stay with good quality op-amps and low impedances in your filters, things should be plenty quiet. 

Things like EFC range, output frequency, phase noise, and intended use  / circuit would be needed to come up with more specific information. 


On Sep 4, 2014, at 10:53 AM, Dan Kemppainen <dan at irtelemetrics.com> wrote:

> Hi all,
> I have an PTI OCXO. The trimming voltage is two pins, with a maximum of
> 6.8VDC across the pins. They specify using a 20K pot as the adjustment
> mechanism. However, I hope to use this thing in a closed loop, and will
> be driving it with an active device.
> What got me thinking is if the frequency trimming is simply a varactor
> across some part of the circuit. I wonder how susceptible is the input
> to driving impedance and noise?
> Any suggestions on how to drive this input, or what to watch out for.
> I'm sure every OCXO is different. Are there any general precautions to
> take?
> Thanks,
> Dan
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