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

[paul swed]

And given the age of many OCXOs it was sort of the tool of the time. There
really were not better devices in the 60s and early 70s.
Regards
Paul
WB8TSL

On Sat, Dec 25, 2021 at 11:43 AM Andy Talbot <andy.g4jnt at gmail.com> wrote:

> In the (very) few OCXO circuits I've seen, voltage at both ends of the
> tuning varactor are derived from the same internal voltage reference.  So
> any drift in this will, partially at least, cancel out.    I too was
> surprised to see nothing more than a Zener being used in one case, but
> bearing in mind this was in a temperature controlled environment is not as
> bad as a Zener in open air
>
> Andy
> www.g4jnt.com
>
>
>
> On Sat, 25 Dec 2021 at 16:26, Poul-Henning Kamp <phk at phk.freebsd.dk>
> wrote:
>
> > Being also a bit of a volt-nut, I played a bit with the Vref output
> > from some of my OCXO's and must sadly report that they were not
> > spectacular, seen from a volt-nut perspective.
> >
> > In at least once case, an admittedly pretty old OCXO design, the
> > voltage reference was not located in the most well-regulated part
> > of the oven and the chosen chip had pretty bad tempco at the elevated
> > temperature.
> >
> > --
> > Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
> > phk at FreeBSD.ORG         | TCP/IP since RFC 956
> > FreeBSD committer       | BSD since 4.3-tahoe
> > Never attribute to malice what can adequately be explained by
> incompetence.
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