[time-nuts] What sort of oscillator is this?

Said Jackson saidjack at aol.com
Sun Sep 28 13:40:32 EDT 2014


An ocxo has two effects that cause a frequency change after power on: heater stabilization and crystal retrace.

Heaters usually stabilize quickly (1 - 2 minutes for DIP-14 ocxo, 7 to 10 minutes for typical eurocan docxo's) and then a. ~30 minutes soak until the ocxo starts following ambient temperature.

After the initial warmup the crystal goes into an exponential retrace as it out-gasses etc and it can take many hours or even days or weeks for that to subside. Then what is left is typically linear aging.


Sent From iPhone

> On Sep 28, 2014, at 3:16, Hal Murray <hmurray at megapathdsl.net> wrote:
> drkirkby at kirkbymicrowave.co.uk said:
>> Two people responded - one says a OCXO and the other an TCXO!!
>> The warmup time is I think an hour, but clearly that is not the time for an
>> oven to warm up.
> An hour seems like a reasonable OCXO warm-up time to me.  You might get 
> faster warm-up times, but you will probably pay for it someplace else.  Here 
> is a graph:
>  http://www.megapathdsl.net/~hmurray/time-nuts/Drift-ocxo3mhz-a.gif
> Also, it probably depends upon how long it has been powered off.
> See how much power the system draws when plugged in but turned off.  Most 
> gear using OCXOs keep them powered up when the front panel switch says "off". 
> So 0 is a strong indication that you have a TCXO.  You can also unplug it 
> for a couple of hours, then watch the power after you plug it in.  I'd expect 
> a step decrease in power after the core is mostly warm.
>> I find it odd that an instrument that probably cost $50,000 when new did not
>> have a TCXO as standard,  and perhaps an oven as an option. 
> Maybe most customers have a good lab source of 10 MHz and use an external 
> clock.
> -- 
> These are my opinions.  I hate spam.
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