[time-nuts] HP Z3801 RB fun

paul swed paulswedb at gmail.com
Tue Dec 27 20:33:16 EST 2016

OK so could not resist. The replacement of the HP 10811 with a PIEZO ocxo
went very well. So in for a penny in for a pound. Why not an RB. Having a
few around. Choice efratom FRS-c. Lot of thought went into this choice. Not
really it was there. It has a inverse frequency to EFC voltage just like
the piezo and opposite the HP 10811.
Well it connects runs and locks using the simple 1 opamp level ofset and
and phase inverter.
But locked is a funny comment. According to HPsatstat and LH. Its pll is
locked. But both scope and the LH graph shows a very slow frequency drift
that with the offset I can make positive or negative. A cycle at 10 ns
takes quite some time about an hour compared to a TBolt and another non
modified Z3801. At this level of resolution some things start to become

I almost wonder if the modified z3801 under some level of drift assumes
everything is locked and fine. Can it be pushed beyond expectations. I
suspect it can.
Anyhow as I say a bit of GPSDO fun.

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