[time-nuts] Re: Why do have OCXO a Vref output? (was: help reviving Trimble UCCM-LPS GPSDO)

[Wilko Bulte]

> On 23 Dec 2021, at 18:47, Attila Kinali <attila at kinali.ch> wrote:
> 
> On Thu, 23 Dec 2021 14:42:27 +0100
> Wilko Bulte <wilko.bulte at xs4all.nl> wrote:
> 
>> A quick experiment learned that the OCXO freq responds to the EFC voltage. 
>> So, looks like the Vref circuit in the OCXO has died.
> 
> A stupid side question: Why do have OCXO a Vref output in the
> first place?
> 
> I can see that some form of reference might make stabilizing
> the power in the crystal easier, but that still wouldn't make
> it necessary to have an actual reference output.

Well, an external disciplining circuit might make good use of a oven stabilised reference, at least that is what I assume?

Disciplining circuit uses Vref from the OCXO for a DAC that in turn drives the EFC of the OCXO. 

No doubt someone will correct me if that is a wrong assumption :-)

> And related to that: Would supplying the voltage reference
> externally, in case of a broken Vref output, work for whatever
> is inside that needs this reference voltage?

Well, currently I have a 2.5V Vref externally connected. No smoke as of yet 

Wilko

> 
>            Attila Kinali
> 
> -- 
> The driving force behind research is the question: "Why?"
> There are things we don't understand and things we always 
> wonder about. And that's why we do research.
>        -- Kobayashi Makoto
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