[time-nuts] Why using HP5370 ext-ref is (maybe) a bad idea

Poul-Henning Kamp phk at phk.freebsd.dk
Sat Mar 1 16:38:47 EST 2014

In message <CAE3hgTd5UDz_-T5mvgBarYYyuLwn=+00p1Fho2Fs+T1p1xdGLQ at mail.gmail.com>
, Brian Lloyd writes:

>Instead of using the external reference input, any thoughts on actually
>disciplining the internal OCXO to bypass the problem?

The end result would be no different than using ext-ref.

Right now I think the best approach to "smear" the error out, is
to run ext-ref from a frequency which is well-known, but not
synchronous with the input signals, for instance from a synth like
the 3336 or a carefully mis-tuned GPSDO

The EFC pin on the OCXO in the 5370 is grounded in a way that makes it
quite hard to unground.

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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