[time-nuts] OCXO Vref (in)stability plot

[Didier]

What is the bandwidth of the measurement?

It may be some broadband noise that is filtered by the OCXO

Didier KO4BB 

Poul-Henning Kamp <phk at phk.freebsd.dk> wrote:

>
>Ok, this surprised me a LOT!
>
>I used my HP3458A to measure the stability of the Vref output from
>an IsoTemp OCXO-107 and the results were anything but stellar:
>
>The OCXO's Vref has 18 microVolt RMS noise
>
>For comparison my HP6626A power-supply has 2 microVolt RMS noise.
>
>Obviously, the Vref only has to be good enough to not be a relevant
>source of noise when used on the EFC input.
>
>If the OCXO has a EFC sensitivity of 10PPM/Volt, then a microVolt
>more or less means a 1e-11 change in frequency.
>
>The Vref is also quite sensitive to the OCXO supply voltage, but
>since it was powered by the HP6626A, that's not where the noise
>comes from.
>
>Plot attached...
>
>
>-- 
>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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