[time-nuts] HP5370B anomaly

Poul-Henning Kamp phk at phk.freebsd.dk
Mon Dec 27 08:06:09 UTC 2010


In message <4D180D2E.9080302 at rubidium.dyndns.org>, Magnus Danielson writes:

>When measuring a pair of OSA 8600 oscillators with a HP5370B I see an 
>oscillating behaviour. It's a stable variation of about 5,5 s.
>I have tried different settings but no luck. I've used the PPS as start 
>and as External Arming. Very stable pattern.

I've seen stuff like it and correlated it to the mains frequency beat
tone against the DUT frequency.

5.5s would correspond to mains being 0.18Hz off:

	50 Hz nominal * 5.5s = 275 cycles

	1/275 * 50 Hz = 0.181818... Hz

Never found out where or how mains got involved however, could be anything
at the level I measured it, even microphonics from the fan.

Poul-Henning

-- 
Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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